Bullet Setback in Sig P365/X/XL/SAS

[Alllen Bundy]

Continuing from:
My Journey From Sig P365 to P365X and Modifications Beyond
(https://www.thehighroad.org/index.p...nd-modifications-beyond.891955/#post-11996270)
P365/X/XL/SAS Grip Module Modifications
(https://www.thehighroad.org/index.php?threads/p365-x-xl-sas-grip-module-modifications.892045/)
Extending the magazine release button Sig P365/X/XL/SAS
(https://www.thehighroad.org/index.p...zine-release-button-sig-p365-x-xl-sas.892113/)
Weighting the P365/X/XL/SAS Grip Module.
(https://www.thehighroad.org/index.php?threads/weighting-the-p365-x-xl-sas-grip-module.892243/)
Polishing the Stripper Rail - Sig P365/X/XL/SAS
(https://www.thehighroad.org/index.php?threads/polishing-the-stripper-rail-sig-p365-x-xl-sas.892413/)
Recoil Spring Assemblies, Sig vs Rival Arms/ISMI for P365/X/SAS
(https://www.thehighroad.org/index.p...sig-vs-rival-arms-ismi-for-p365-x-sas.892594/)
Failure to Return To Battery Prevention - P365/X/XL/SAS
https://www.thehighroad.org/index.p...n-to-battery-prevention-p365-x-xl-sas.892742/

Bullet Setback in Sig P365/X/XL/SAS

There seems to be some debate about how serious bullet setback actually is. There also seem to be a lot of opinions about chat causes bullet setback. Someone had commented that a Makershot magazine loader caused his ammunition to setback. I also use the Makershot loader for the Sig P365/X/XL/SAS, so I thought I'd better check it out and also test a few other things to see what will actually cause bullet setback.

For the first test I used Remington Range 9mm 115 gr FMJ. I loaded a 12rd Sig X/XL magazine to 11 rds with the Makershot loader. I measured the 12th round with a caliper and then also loaded it with the Makershot loader. I removed the cartridge, measured it's overall length. I repeated this for a total of 10 tests. No measurable setback.

I continued using the same cartridge for the next test. I loaded the 12th round with the Makershot loader. Then inserted the magazine against a closed slide. I pulled the slide rearward and locked it back. (This is especially difficult with a new Sig magazine) I removed the magazine. I removed the 12th round, measured it's overall length. I repeated this for a total of 10 tests. Again, NO measurable setback. This same cartridge had been loaded a total of 20 times as the 12th round using the Makershot loader with NO setback.

I continued using the same cartridge for the next test. I loaded the 12th round with the Makershot loader. I loaded the magazine with the slide locked back. I released the magazine to chamber a round. I removed the magazine, ejected the round in the chamber and measured it's overall length. I repeated this for a total of 20 tests.

After the 3rd chambering from the magazine, the bullet began to setback. After the 20th test the bullet had setback a total of 0.0150".

I repeated the chambering test with Winchester Silvertip 9mm 115gr JHP. After the 5th chambering it setback 0.0005". By the 20th round it had setback a total of 0.0070"

I repeated the chambering test with MagTech 9A 9mm 115 gr FMJ. After the 11th chambering the bullet had setback 0.0005". But further chambering caused the bullet to move FORWARD in the case. After the 20th chambering the bullet had moved forward a total of 0.0030". This wasn't a fluke as I performed other chambering tests with the MagTech ammo and it also began to set-forward.

I repeated the chambering test with Speer LE Gold Dot 9mm 115 gr JHP. After the 20th chambering it may have setback 0.0005" But this could have been a measuring error. No practical setback.

I repeated the chambering test with Sig Elite Performance 9mm 115 gr JHP. After the 20th chambering it may have setback 0.0005" But this could have been a measuring error. No practical setback.

During my testing of the P365 I noted that the MagGuts 12+2 magazine spring kit had a magazine follower design that was inferior to the Sig design. While the Sig follower required a uniform amount of force to chamber a round, no matter if it was the first round in the magazine or the last, when the MagGuts modified magazine was down to the last few rounds it could require as much as double the amount of force to chamber a round. This was caused by the follower not presenting the cartridge at a favorable angle to align with the firing chamber. The amount of force required to chamber the last few rounds was also erratic.

When I tested cartridges for setback when chambering from the MagGuts modified magazine, the amount of setback per chambering could vary considerably, whereas with the Sig magazine, as soon as any setback began to occur, it was a fairly similar amount of setback every chambering.

What my testing has shown is that with any reasonable quality ammunition, setback will likely only be an issue if you are chambering the same round from the magazine multiple times. This is mainly an issue for people that carry with a round in the chamber loaded from the magazine, and then remove the magazine and eject the round and then later reload with the same round that was ejected.

This setback is completely avoidable with a P365/X/XL/SAS if you manually chamber the first round and then release the slide onto the round, and then insert a magazine. Manually loading will NOT harm a P365/X/XL/SAS, as the extractor claw face is beveled and the extractor is spring loaded and mounted on a pivot.





If you are worried in the least about excessive wear to the extractor claw, while manually loading, you can slowly release the slide onto the cartridge and then press the rear of the extractor inward, which will then pivot the extractor claw outward and allow the recoil spring to pull the slide into battery.



But beware that some older designs, such as the 1911, may suffer extractor breakage if you try to chamber a round manually.

I have not yet seen any definitive information as to whether or not bullet setback can cause any damage to a P365/X/XL/SAS. But for now I will just avoid the bullet setback issue entirely by chambering the 1st round manually.

While this information is specific to the P365/X/XL/SAS, it might also be relevant to some other models and brands.

If you have seen any good testing on bullet setback, please post a link to the information.

If you are planning to do any bullet setback testing of your own, it would be safest if you remove the firing pin before doing any testing.

Next: Sig P365X/XL 12 rd Magazine vs MagGuts 14 rd Spring Kit.

 

[Drail]

Bullet setback IS a serious problem in cartridges that run high pressures and can cause serious injury in a semi auto pistol. I have seen it.You should NEVER chamber a factory round more than once. Every manufacturer will tell you this - they are intended for one chambering only. The problem is almost never the gun - it is poorly constructed ammunition - namely insufficient case neck tension. The bullet is not held in place by the crimp - it is held by tight tension by case mouth - the entire length of the case mouth - not just the last couple of hundredths. A lot of cases used in factory ammo are overexpanded or undersized. Every pistol caliber die set I own came with expander buttons that over expanded the case mouths. I had to turn them down to get them 3 or 4 thous. under bullet diameter and that solved the problem. If you handload check you bullet's actual dia. - if your expander button is not 3 or 4 thous. under that your bullets will move. If you seat a bullet in a case but do not crimp it and then press it as hard as you can into the edge of your bench it should not move ANY. If it does you have a loose fit and you will experience bullet setback or pull. I have .45 dummy rounds that I used for many years to test guns I was working on and they never setback any after I got my expander turned down to fit the bullet dia. Those rounds were hand cycled through a lot of pistols to test feeding. They're still in spec. Sizing your expander button will also stop revolver bullets from pulling forward.

 

[Alllen Bundy]

You should NEVER chamber a factory round more than once. Every manufacturer will tell you this - they are intended for one chambering only.

While my testing has shown that some brands of defensive ammo, such as Sig and Speer, are unlikely to have setback problems, some brands do have setback issues. It is better to be safe than sorry.

In case anyone was wondering, any rounds that I've used for setback testing and any rounds that I have chambered from the magazine, but not fired, will have the bullets and powder removed. I'm also measuring every cartridge in a box and weeding out the most undersized cartridges, of which I will remove the bullets and powder. I'll use the empty shell cases with intact primers for striker/firing pin testing.

I plan to epoxy the unused bullets into spent shell casings, drill holes through the sides of the shell cases and use them for dummy rounds. Waste not want not.

 

[Otto]

Repeatably chambering a round is a poor and inconsistent test for setback.
And to properly load a P365, refer to page 21 in your owner's manual.

 

[Alllen Bundy]

Repeatably chambering a round is a poor and inconsistent test for setback.
And to properly load a P365, refer to page 21 in your owner's manual.

Page 21 is the table of contents and it does NOT include loading instructions.

The Sig manual lists one method of inserting a magazine. HOWEVER, SIg also advertises the P365/X/XL/SAS as a 10+1, 12+1, and 15+1 depending upon the magazine. That means that you need to load one cartridge in the firing chamber and THEN insert the magazine loaded to capacity into the P365/X/XL/SAS with a CLOSED slide in battery.

It doesn't matter what kind of repeatable setback testing that you do on the bench. Chambering a round from the magazine is a REAL WORLD SETBACK TEST. It's the ONLY setback test that matters for YOUR pistol. (Other than a setback due to a malfunction) It doesn't matter what kind of setback occurs in a Glock if YOU have a Sig.

 

[Slamfire]

This RIA ejected magazines when new



the magazine latch was either insufficient, or as I now suspect, held the magazine too high. As the slide went forward, the magazine was ejected down! RIA sent me a replacement, this was the old one



Magazines sat in the pistol very low with the replacement mag release. Lots of clearance between bottom of magazine and bottom of grip. Also, I could feel a very distinct bump, bump, as cartridges fed into the chamber. If I reloaded the bullet several times, the bullet was shoved deeper into the case each loading. The bump, bump had to be the bullet hitting the feed ramp, and finally chambering.

Then one day, this happened. The round fired, the magazine and all its contents ejected, and I had a case with a blown case head in the pistol.







I did not know if it was my reloads or not. I chronographed and targeted the load, and it did not seem excessive.n This is the load.



The pistol, once I racked the slide, the slide moved freely back and forth. My beautiful replacement coco bolo grips were cracked. The magazine base spring disappeared, and something hit my chin and caused a bruise, something hit the roof over the firing line. Unfired rounds in the magazine had the bullets stuffed in the case. Since I had flying springs, bullets, I am glad I always wear glasses! Could have gotten something in the eyeballs.

I disassembled the RIA, wiped everything out, and reoiled. The slide racked, the hammer fell, the pistol was operable. So I loaded up a different batch of ammunition and shot that. Everything worked. Because I was uncertain about the ammunition, it took time for me to shoot the kaboom batch up, but when I did, it all went bang. Before I shot up the kaboom batch, I cut my loads by 3 tenths of a grain to this load, and shot an ammunition can of it. This reduced load has to be a mild load. I was very careful about my reloading procedures.



And what do you know, before the ammunition can of the reduced load was empty, I got a high pressure round. The primer flowed back into the firing pin hole, the case stayed on the bolt face, and the slide was jammed back.

This pistol is made of 4140 steel, and I am certain had I been firing some WW1 relic, made from un heat treated plain carbon steels, I could have ended up with a bulged or bent slide. But this thing, all I have had to do, is field strip, wipe out the powder residue, reassemble, and it functions. Today's guns are built much better.

That was when I decided that while bad reloads were still a could be, bullet set back was something to worry about, and fix. I purchased an EGW higher magazine catch and installed it. Sometimes I get bullet set back, but overall, not enough to cause a high pressure incident. Keeping my fingers crossed.

And I did completely shoot up the blowup batch, and nothing bad happened. Due to case weight variations, it is fruitless to attempt to weigh pistol rounds. Loaded rounds vary more by four grains, so you are never going to catch a double charge, or an excessive charge, by weight.

 

[herrwalther]

This pistol is made of 4140 steel, and I am certain had I been firing some WW1 relic, made from un heat treated plain carbon steels, I could have ended up with a bulged or bent slide. But this thing, all I have had to do, is field strip, wipe out the powder residue, reassemble, and it functions. Today's guns are built much better.

Fortunately for you, 45ACP is a relatively low pressure cartridge. Max 21,000 PSI compared to 35,000 9mm. In my experiences and tests with setback rounds, 45ACP is much easier to set back than other calibers. But less danger by comparison. Strong pistol construction helps too.

I don't worry about setback all that much. I keep my carry firearm chambered. It only gets unloaded when I am cleaning them. Before it gets loaded again I will pull out a minimum of 3 rounds (or the whole thing) and line up the cartridges on a level surface. If I see any rounds that look shorter than the others, I will take measurements with calipers. Short ones get tossed out. And the +1 round that was chambered before cleaning gets put back in the magazine at a random location.

 

[Tirod]

If a pistol carries 6 or 7 rounds, then topping off with one in the chamber makes a small improvement. Lots of people picked up on this practice about ten years ago, 7 + a spare = at least 13 with a mag change.

The P365 with 11 plus a spare = 21, at least, which in quantity deletes a mag change. The difference adding one more round when you carry 20 is a lot less important than when you carried 12. Consider the 14 shot mags - 15 + a spare = 29. The incremental value of one more round is reduced even more, and the hassle of loading a mag on a closed slide - SIG 12 round mags being problematic - is eliminated.

We have arrived at a point where loading the extra bullet has less value and has become a tradition, not a tactical necessity. In military use it's pretty much ignored, LEO's carry at least two mags in their duty guns which often have more than 15 each. Carry weight has long been a problem for cops with increasing loads causing back injury over time and disability - which taxpayers insure.

Another case of police practices not working well for civilian carry.

As for case setback, use crimped ammo. Since it is a concern, not using loose rounds in open necks is the solution, rather than extensive modification of a pistol. Military issue is - pistol or rifle. Since the three causes of malfunction in a firearm are magazines, ammo, and operator error, don't make the error of choosing ammo which is a known cause of problems. Another cause of setback? Constantly loading the same round repeatedly into the chamber. The question being, why? Load the gun and leave it. We all should be practicing safety as if it were loaded, constant unloading and reloading is the manipulation of the firearm which is listed in the top 3-4 reasons it's negligently discharged, a much more frequent problem than a compressed round. Again, operator error.

Manufacturers have more than a few well paid engineers, along with an extensive institutional history of what not to do wrong. While in certain cases it could be argued they mess up, for the most part over the last century the longer lived companies avoid most of the situations we blunder into, and their instructions are well meant to keep us from making errors in judgement which contribute to incidents of negligence. The idea we need to load an extra round has much less importance with higher capacity magazines, and using quality auto pistol ammo should cover the rest. It goes to, just because we can, doesn't mean we should. Changing our practices and outdated habits can and often does create a better solution.

 

[Alllen Bundy]

The incremental value of one more round is reduced even more, and the hassle of loading a mag on a closed slide - SIG 12 round mags being problematic - is eliminated.

Here is an interesting data point. It takes MORE force to insert a Sig 12 rd mag loaded with 11 rounds than it does to insert a MagGuts modified magazine loaded with 13 rounds.

In the tests that I performed, a Sig 12 rd mag loaded to 12 rounds required 40% more force to insert than MagGuts modified magazine loaded to 14 rounds. Yet the MagGuts modified magazine still had as much spring force as the Sig magazine at the last round in the magazine. A MagGuts modded magazine greatly reduces issues with inserting a magazine loaded to capacity against a closed slide.

Polishing the stripper rail also makes racking the slide against a magazine loaded to capacity more manageable.

The idea we need to load an extra round has much less importance with higher capacity magazines, and using quality auto pistol ammo should cover the rest...................... We have arrived at a point where loading the extra bullet has less value and has become a tradition, not a tactical necessity.

Besides the inevitable Zombie apocalypse, we now have to deal with mobs of "Peaceful Protesters". (I live in Minneapolis, home of defunding the police.) Every round before you need to reload may be important. For all you know your backup magazine could fail.

Another cause of setback? Constantly loading the same round repeatedly into the chamber.

I can manually chamber a round manually in a P365/X/XL/SAS over 100 times with NO measurable setback. The setback occurs when you chamber a round from the magazine.

The question being, why? Load the gun and leave it.

You may need to remove your defensive ammo from the magazine to shoot FMJ at the range. Or you may wish to remove the ammo at home for safety reasons. You may keep a loaded mag handy that you can load quickly if necessary. I'm sure that there are many other reasons. In my case I've been doing considerable testing on my P365X and I not only unload it, but I have also removed the firing pin for many tests that I have performed.

It goes to, just because we can, doesn't mean we should. Changing our practices and outdated habits can and often does create a better solution.

I'll agree that there are often problems with the status quo. But you should always look for the root cause of the problem. Altering your behavior to compensate for a problem in your weapon is a Bandaid fix at best. But sometimes you have no choice.

Clearly, some brands of ammo are nearly immune fro+m setback issues and other brands are very susceptible to setback. But a minor behaviour modification, such as chambering the 1st round manually, eliminates the possibility of bullet setback when chambering a round multiple times.

Using a better magazine design greatly reduces magazine insertion force. Performing finishing work on your pistol that was NOT done at the factory can greatly reduce racking force and improve reliability.

I never trust the tires that come stock on a new car to be great performers, as they usually are not. Replacing the tires is the first change I would do. So why should I trust Sig to provide me with the best magazine design?

 

[Alllen Bundy]

I received a bullet remover today and pulled 8 bullets of six different models/brands of ammo for a total of 48 bullets.

The Sig Elite Performance V-Crown JHP 115 gr bullets were the most difficult to remove, requiring 8 to 12 hard whacks in the bullet remover before the bullets came out. You can see a significant amount of scratching around the butt end of the bullet where it was inside the case, suggesting there was a significant interference fit. It also appears that the bullets were seated further inside the cartridge than the other brands, with more area inside the shell case to hold the bullet in place.

The Speer Gold Dot JHP 115 gr, required 3 to 5 hard whacks in the remover to extract the bullet. The Speer also had a significant mount of scratching on the butt end of the bullet, but it was not set as deeply inside the shell case as the Sig. Also, inside the shell case there was a ring of black gunk where the butt end of the bullet would have been, which I suspect is a sealer of some kind.

The Winchester Silver Tip JHP 115 gr bullet required 2 to 3 hard whacks in the remover to extract the bullet. It is necked down in the middle. It gives the illusion that it gets wider just before it tapers to form the tip. However, the butt end measures 0.3545", it necks down to 0.3470" and then widens again to 0.3510" before it narrows to form the tip. Not sure why.

The MagTech 9A FMJ 115 gr required 2 to 3 hard whacks in the remover to extract the bullet. It appear as if it is necked down in the middle, but it measures more like it makes a sudden expansion, instead of actually being necked down.

The Remington Range FMJ 115 gr required 1 to 2 hard whacks in the remover to extract the bullet. It was the most susceptible of the 6 bullets to setback when chambering a round from the magazine

The Winchester White Box FMJ 115 gr required 1 to 2 hard whacks in the remover to extract the bullet.

It's not too surprising that the Sig and the Speer bullets that were the most difficult to remove also had the least amount of setback during my testing.

Left: Sig EP-V-Crown - - - - Middle: Speer Gold Dot - - - - Right: Winchester Silver Tip

Left: MagTech 9A - - - - Middle: Remington Range - - - - - Right: Winchester White Box

 

[JohnKSa]

That means that you need to load one cartridge in the firing chamber and THEN insert the magazine loaded to capacity into the P365/X/XL/SAS with a CLOSED slide in battery.

Most of the time the process for loading a pistol to full capacity is to put the magazine in, chamber a round from the magazine, then remove the magazine, top it off and replace it. In fact, I have one semi-auto whose manufacturer specifically indicates direct chamber loading is acceptable but still provides that procedure as the way to load to full capacity.

Examining the extractor and looking at the design is not a reliable way to determine if direct chamber loading is acceptable in a gun. For example, Glocks have a pivoting extractor with a bevel on the forward edge of the hook but direct chamber loading is still not recommended. There are other guns with similar designs that also won't tolerate direct chamber loading.

The rule of thumb is that unless the manufacturer states that direct chamber loading is acceptable, the gun should be loaded from the magazine. It's not uncommon to see competitors carrying a spare mag (often called a Barney Mag) specifically for the purpose of loading the chamber before inserting another fully loaded mag into the gun for the start of a stage.

That also means that "chambering a round" in a semi-auto pistol means chambering it from the magazine unless the context clearly indicates otherwise. When someone talks about direct chamber loading, they will almost always explain what they're doing or just call it direct chamber loading.

As far as setback goes, different ammo is susceptible to differing amounts. I've seen some ammo that will setback noticeably from one chambering. The CCI aluminum cased ammo was really bad about that. Generally speaking, premium self-defense ammo will tolerate being chambered multiple times before any setback occurs.

It's also interesting to note that setback often isn't a linear thing--the bullet may not move at all for the first few chamberings but when it starts to move it can begin setting back significantly after that.

The effect of setback is dependent on the ammo. The heavier (longer) the bullet, the more a given amount of setback will raise the discharge pressure. What might not be a dangerous amount of setback with a very light for caliber bullet could cause really scary discharge pressures if the bullet is on the heavy end of the scale for the caliber.

 

[sparkyv]

WOW! That's quite a bit of turning!

Every pistol caliber die set I own came with expander buttons that over expanded the case mouths. I had to turn them down to get them 3 or 4 thous. under bullet diameter and that solved the problem. I

EEEK!

Then one day, this happened. The round fired, the magazine and all its contents ejected, and I had a case with a blown case head in the pistol.

Since the P365 has a witness hole, I load it and leave it be. Then periodically, say a few times per year, I shoot it as-loaded to verify my real-world carry performance with my actual CC ammo. Then I shoot up my practice ammo.

Another cause of setback? Constantly loading the same round repeatedly into the chamber. The question being, why? Load the gun and leave it.

You may need to remove your defensive ammo from the magazine to shoot FMJ at the range.

 

[WYO]

I will re-chamber factory Gold Dots a few times before putting them in the practice pile. That includes those used in a P365 and P365XL as well as Glocks, and I chamber a round using the slide release with the full magazine seated and the slide locked open. The difference between the used rounds and factory rounds in those instances are only a few thousandths of an inch. No worries.

You should NEVER chamber a factory round more than once. Every manufacturer will tell you this - they are intended for one chambering only. The problem is almost never the gun - it is poorly constructed ammunition - namely insufficient case neck tension.

I have never seen a box of ammo with a warning stating that rounds may only be chambered one time. If I had, I probably would avoid that ammo.

 

[Drail]

No one prints it on the box but all of them will tell you not to do it if you ask them.

 

[JohnKSa]

I can't produce the source now, but I recall reading an article some years ago in which the author interviewed a major ammunition company. The rep indicated that they felt that their premium self-defense ammunition should withstand 4 chamberings without setback. I can't remember the company now. I also can't remember if the rep said that there was no guarantee against setback from rechambering practice ammo or if that topic just never came up.

I've taken that claim to mean that the major ammo companies are aware of the problem and that in general premium self-defense ammo shouldn't set back from a rechambering or two or four, but I will admit that could be an overly optimistic interpretation.

The safest thing to do is to not rechamber ammunition.

Next safest is to do testing (like the OP) to determine how resistant that a particular loading is in a particular gun and then stay well inside the discovered boundaries. It is important to keep in mind that different guns can have a different effects on setback due to their magazine/feedramp designs and so assuming that just because a load doesn't setback in one gun it won't setback in any gun is a mistake.

 

[Alllen Bundy]

Examining the extractor and looking at the design is not a reliable way to determine if direct chamber loading is acceptable in a gun.

I beg to differ. It can actually be a fairly good method, depending upon your analytical skills.

You first need to determine whether or not the extractor claw can in fact pivot outward far enough to allow the cartridge rim to pass by. On a Sig P365/X/XL/SAS, pressing the rear of the extractor inward causes the extractor to pivot and move the extractor claw outward far enough that the extractor claw clears the shell case lip and the recoil spring pulls the slide closed. This means that an interference problem does not exist in the P365/X/XL/SAS.

The only problem that you could incur would be chipping the extractor claw edge, if the extractor claw was sharp and it was also heat treated so hard that it was brittle. This is extremely unlikely with modern pistol designs. But this is also why you should make sure that the extractor claw edge is dull, and if sharp, dull the edge.

Directly chambering a round in this manner is highly unlikely to cause any damage to the extractor claw in a Sig P365/X/XL/SAS

Next you need to determine if pushing the extractor forward against shell case lip can cause it to move outward and out of the way allowing the extractor to move past the shell case lip.

If the forward edge of the extractor is flat, then obviously the slide slamming the extractor into the shell case lip will not work and may possibly damage the extractor.

If the forward edge of the extractor is significantly beveled, then the shell case rim will exert a sideways force upon the extractor to move it out of the way.

In the case of the P365/X/XL/SAS, the bevel on the leading edge of the extractor is approximately 45°. That means that about 1/2 of the force applied to the extractor will be pushing the extractor outward while the other 1/2 of the force will be pushing the extractor claw backward. The amount of force required to move the extractor claw over the shell case lip will be determined by the strength of the extractor spring multiplied by the leverage gained or lost by the extractor, plus a bit of extra force to overcome any friction between the shell case lip and the extractor.

In the case of my P365/X/XL/SAS, with my thumb I can push the slide forward, moving the extractor claw over the shell case lip and closing the slide. You can also slap the back of the slide to move the extractor over the shell case lip. It's just not that much force being applied to the extractor, and extremely unlikely that it can be broken this way.

If the extractor edge was sharp, then you could easily either chip the edge of the extractor if it was brittle, or if the steel was too soft, bend over the edge of the extractor claw and form a burr. Which is why, in any event, you should make sure that the extractor claw edge is dull, and if sharp, dull the edge.

The P365/X/XL/SAS extractor may be hardened to some degree, but it is still soft enough to file, so it isn't so hard that it is brittle.

Since about 1/2 of the force being applied against the extractor is trying to move it backwards, you need to consider the double sheer strength of the pivot pin of the extractor. In the case of the P365/X/XL/SAS, even the lightest duty coiled spring pin available has a double sheer strength of 475 lbs. Since about 1/2 of the force applied to extractor is being diverted outward, that means that you would need to apply 950 lbs of force to the leading edge of the extractor to sheer the pivot pin. My thumb cannot apply anywhere near that much force to the slide, yet it was still enough to move the extractor claw over the shell case lip.

Directly chambering a round this way is extremely unlikely to shear the pivot pin.

Lastly you need to consider whether or not releasing the slide quickly onto a round in the chamber can increase the force enough upon the extractor claw and the pivot pin to break either. Force = Mass x Acceleration. The faster that the slide moves the extractor against the shell case lip, the greater the force applied to the extractor claw and the pivot pin.

My general mechanical experience suggests that this is also not likely to break the extractor claw or the pivot pin. My actual experience has shown that it hasn't damaged the extractor or the pivot pin in my P365X.

The rule of thumb is that unless the manufacturer states that direct chamber loading is acceptable, the gun should be loaded from the magazine.

I disagree. The rule of thumb should be to NEVER assume.

Just because a manufacturer doesn't mention something doesn't mean that it isn't acceptable. What a company publishes is often determined by their liability lawyers. If you are really concerned, ASK the manufacturer if directly chambering a round is acceptable. But also take their answer with a grain of salt. Companies are operating in THEIR best interest, NOT yours. Also consider that manufacturers will sometimes give you bad or incomplete information. Sometimes they don't know the answer. Sometimes they even lie.

As I have described, using a P365/X/XL/SAS, directly chambering a round, gently releasing a slide onto the cartridge, and then pressing on the rear of the extractor so that the extractor claw swings outward and allows the recoil spring to close the slide, is just not going to damage the extractor. Directly load the same cartridge a thousand times and it is still not going to setback even a thousandth of an inch or damage the extractor. In terms of wear, the steel extractor wins over the brass shell case every time.

If directly chambering a round would damage a P365/X/XL/SAS, Sig would very likely publish a warning against it. But they don't. In Sig's manual they recommend inserting the magazine into an open slide. But they also advertise the P365/X/XL/SAS as a 10+1, 12+1 and 15+1, depending upon the magazine capacity being used. But that requires inserting a magazine loaded to capacity against a closed slide, and Sig makes no mention of that in their manual.

This is an example of when you need to re-examine the status quo. Some 100+ year old designs, such as the 1911, were NOT designed to be manually chambered and may in fact be damaged by manually chambering. But I contend that this is a deficient design that has been rectified by many newer designs, such as the Sig P365/X/XL/SAS.

For example, Glocks have a pivoting extractor with a bevel on the forward edge of the hook but direct chamber loading is still not recommended.

There is a big difference between not recommended and recommending NOT to do something. Does Glock actually say that direct chambering will cause damage in their pistols?

There are other guns with similar designs that also won't tolerate direct chamber loading.

If a modern semi-automatic won't tolerate direct chamber loading I would wonder what other issues it may have and consider that a possible reason not to buy it, when you can instead buy another brand without that deficiency.

It's not uncommon to see competitors carrying a spare mag (often called a Barney Mag) specifically for the purpose of loading the chamber before inserting another fully loaded mag into the gun for the start of a stage.

That seems like extra work if you can directly chamber the round instead.

 

[murf]

running a flat extractor over a round case rim does not lend this process to easy calculation. i side with @JohnKSa in this discussion.

murf

p.s. great discourse on bullet setback, by the way.

 

[Otto]

There is a big difference between not recommended and recommending NOT to do something. Does Glock actually say that direct chambering will cause damage in their pistols?

I'm beginning to sense that you started this thread just to argue with people.

 

[herrwalther]

No one prints it on the box but all of them will tell you not to do it if you ask them.

There are also companies that say don't put loaded firearms in a quick access safe designed for self/home defense. Any halfway decent company related to firearms is going to have lawyers recommending not to do something, knowing full well people will anyway. Corporations have to play CYA with the overly litigious society we have become.

I have tested a lot of ammo about bullet setback with my method outlined earlier. Cheap, range brass like Blazer as well as budget HPs like WWB are most prone to setback. Makes sense as they are the cheapest rounds of both types available. The common SD rounds with a cannelure are the most resistant to setback. SD rounds with cannelures are common in XTP and HST rounds. This is not an absolute rule of thumb however. Premium SD rounds without a cannelure like Golden Saber and Gold Dot have held up well in my own setback tests.

The best peace of mind you can have about setback is do your own testing. All you need is at least one round and some calipers. Measure the overall length of the cartridge before then chamber it one to a dozen times. Look for a change. Bullets from the factory will have their own variances in overall length, a few thousandths of an inch. Significant change will depend on the caliber of the round and the advertised pressure. Relatively low pressure rounds like 45ACP can take more setback before becoming unsafe than a high pressure round like 9mm.

 

[Alllen Bundy]

The heavier (longer) the bullet, the more a given amount of setback will raise the discharge pressure. What might not be a dangerous amount of setback with a very light for caliber bullet could cause really scary discharge pressures if the bullet is on the heavy end of the scale for the caliber.

I think that a longer cartridge is more likely to setback and to setback further per chambering, because the bullet tip will contact the feed ramp sooner before the cartridge is more optimally aligned with the chamber, which will increase the chambering friction, which will likely increase the amount of setback.

It is important to keep in mind that different guns can have a different effects on setback due to their magazine/feedramp designs and so assuming that just because a load doesn't setback in one gun it won't setback in any gun is a mistake.

Not only can the setback vary from one model pistol to another, but it can also vary from one brand of magazine to another. The last couple of rounds in the MagGuts magazines that I tested could require as much as double to force of the stock Sig magazine to chamber a round and could result in even greater setback.

It's also interesting to note that setback often isn't a linear thing--the bullet may not move at all for the first few chamberings but when it starts to move it can begin setting back significantly after that.

With the Remington Range FMJ, it started to setback with the 3rd chambering at about 0.001" per chambering until the 12th chambering, then the amount of setback slowed down until the 16th chambering when it stopped setting back any further with the next 4 chamberings.

But when the same ammunition was chambered, as the last round in the MagGuts magazine, the amount of setback per chambering was very erratic, which also correlated with erratic chambering force measurements.

I think that it's fair to say that the amount of setback is unpredictable from brand to brand of cartridge, from model to model of pistol, and brand to brand of magazine.

 

[JohnKSa]

I beg to differ. It can actually be a fairly good method…

If by “fairly good” you mean it will work some of the time, I agree. If by “fairly good” you mean reliable, then no, it’s not.

The only problem that you could incur would be chipping the extractor claw edge, if the extractor claw was sharp and it was also heat treated so hard that it was brittle. This is extremely unlikely with modern pistol designs.

In fact, a common issue with direct-chamber loading in pistols not designed for it is a chipped or broken extractor. Even in modern pistols. Which means that whatever survey or analysis you did to determine it’s “extremely unlikely with modern pistols” might need to be re-evaluated.

My general mechanical experience suggests that this is also not likely to break the extractor claw or the pivot pin. My actual experience has shown that it hasn't damaged the extractor or the pivot pin in my P365X.

Your actual experience has shown that it hasn’t damaged the extractor or pivot pin in your P365X YET. I really don’t know if that particular gun is designed to tolerate direct-chamber loading or not, and I’m not making any claims about it one way or the other. The key is that you don’t know either. Which brings us to…

The rule of thumb should be to NEVER assume.

Correct. If you want to know if the gun is designed to tolerate it, find out what the manufacturer says—if you can’t find something already published, contact them. You should not assume it is designed to tolerate it.

If you are really concerned, ASK the manufacturer if directly chambering a round is acceptable.

Excellent strategy.

But also take their answer with a grain of salt. Companies are operating in THEIR best interest, NOT yours.

Explain how the manufacturer’s interests, in this case, wouldn’t align with the gun owner’s. It’s not like direct chamber loading is dangerous—it’s not going to incur any sort of liability on their part. In this case, if they tell you not to do it, the only logical reason to do so is because they don’t want the gun to break—which is exactly what you, the gun owner wants too.

Does Glock actually say that direct chambering will cause damage in their pistols?

Glock, as does SIG, provides a detailed, step-by-step process they recommend for loading the gun. They don’t list all the possible ways to load the gun that aren’t recommended. As I recall, direct-chamber loading is mentioned negatively in the Advanced Armorer’s course, but I don’t feel like going through my notes to verify it. You can easily find instances of people chipping/breaking their extractors by direct chamber loading their Glocks.

If a modern semi-automatic won't tolerate direct chamber loading I would wonder what other issues it may have and consider that a possible reason not to buy it, when you can instead buy another brand without that deficiency.

Not to put too fine a point on it, but you really don’t have any idea how common or uncommon it is for modern semi-automatics to be designed to tolerate direct chamber loading. At any rate, fortunately these days the selection of pistols on the market is truly impressive. If direct-chamber loading is a feature that’s important to you, you can certainly find some guns out there that will tolerate it.

That seems like extra work if you can directly chamber the round instead.

Agree. You should probably think about why people go to the extra work.

I think that a longer cartridge is more likely to setback and to setback further per chambering, because the bullet tip will contact the feed ramp sooner before the cartridge is more optimally aligned with the chamber, which will increase the chambering friction, which will likely increase the amount of setback.

The comment you’re addressing is discussing longer bullets (projectiles), not longer cartridges, and the effect of setback (pressure increase) not the likelihood of setback.

I think that it's fair to say that the amount of setback is unpredictable from brand to brand of cartridge, from model to model of pistol, and brand to brand of magazine.

I think that's a pretty fair assessment.

 

[Tirod]

I never trust the tires that come stock on a new car to be great performers, as they usually are not. Replacing the tires is the first change I would do. So why should I trust Sig to provide me with the best magazine design?

I believe this sums up your recommendations. Taking the quote at face value, since the manufacturer usually leaves horsepower and mileage "on the table," then immediately rebuilding the new motor to make improvements is justified?

 

[reddog81]

Load one round in magazine and then slowly ride slide shut if you’re concerned about setback. Then insert full magazine. No setback and the gun is fully loaded.

There’s no good reason to drop a round in the chamber then let the slide slam shut. Just because something can be done doesn’t mean it’s a good idea.

 

[Tirod]

Yet all the other rounds are loaded with the slide stripping off the cartridge and slamming shut. That is the recommended procedure for most military arms, and often described in owners manuals of auto pistols. Most explicitly state "Do not ride the bolt/slide home!"

Again, we are changing how its done best, worrying about a marginal issue that ammo management and some discretion would avoid in the first place. Why are we constantly unloading it, and what should we do with those rounds loaded more than a few times? Apparently the OP thinks it should need extensive modification right out of the box, which is why I asked the question above.

 

[Alllen Bundy]

If by “fairly good” you mean it will work some of the time, I agree.

I was understating the case. If you actually follow the analysis steps that I gave, the results will be considerably better than fairly good. The first step is the most important of all.

You first need to determine whether or not the extractor claw can in fact pivot outward far enough to allow the cartridge rim to pass by."

This step will weed out the majority of pistols that cannot tolerate direct chambering.

On a Sig P365/X/XL/SAS, pressing the rear of the extractor inward causes the extractor to pivot and move the extractor claw outward far enough that the extractor claw clears the shell case lip and the recoil spring pulls the slide closed."

This means that an interference problem does not exist in the P365/X/XL/SAS. If the extractor chips or breaks at this stage, then it IS a POS that is NOT reliable to enough to carry, EVER!

Next you need to determine if pushing the extractor forward against shell case lip can cause it (the extractor) to move outward and out of the way allowing the extractor to move past the shell case lip.

If the extractor does NOT have a substantial bevel on the leading edge, then releasing the slide will likely not return to battery and may damage the extractor, and this direct cambering method will not work.

If the leading edge of the extractor DOES have a substantial bevel, then pushing the slide forward should allow the extractor claw to move outward and pass over the shell case lip. If the extractor chips or breaks at this stage, then it's a POS that is NOT reliable to enough to carry, EVER! If the extractor breaks in this situation it's likely that it could break in normal use as well. Better to find out a potential problem on the bench rather than in a self defense situation.

But before we go further, let's look at the extractor in question. The claw should NEVER have a sharp edge. There is no need for it and sharp edges on the claw will cause excess friction that could add up to a failure to return to battery. Sharp edges are stress risers from which cracks can form, propagate, and allow stress fatigue failures to occur. The most common reason that manufacturers leave a sharp edge, when it's not necessary to the design, is cost. But where reliability is important, sharp edges should be radiused, unless there is a very good reason to keep the edge sharp. With modern metallurgy, there is no need for a pivoting extractor in a modern design to be so hard that it is brittle.

Most people don't have a kit for testing metal hardness. But if metal is soft enough to file, then it is unlikely to be brittle. I tested the extractor in my P365X and while it is fairly hard, it is still soft enough to file.

If the extractor is hard enough to be brittle, I would NOT consider the weapon reliable enough to carry.

Any engineer worth his salt is going to consider both reliability and safety in their design. They will ponder how the end user might operate the pistol in normal AND in abnormal use.

Assume that for whatever reason there was a failure to extract the last round and the slide locked rearward because the magazine was empty. The shooter was done for the day, didn't realize that the shell case failed to extract, and instead of reloading just releases the slide. If the extractor breaks it is a crappy design.

Could the user easily manually insert a cartridge into the chamber? If yes, then your design should not result in breakage if the user releases the slide onto the cartridge.

Assuming that extractor has passed the analysis so far, and the extractor is not brittle, and/or the claw is not sharp, and/or not made from a substandard material, the last remaining question is: "Can the the recoil spring accelerate the extractor forward to a velocity sufficient to damage the extractor?"

Your actual experience has shown that it hasn’t damaged the extractor or pivot pin in your P365X YET.

How many directly chambered rounds, without breakage of the extractor, would you consider adequate to qualify as reliable? I've got the time to test. I just finished epoxying 16 bullets into spent shell cases to make dummy cartridges. And I've got a spare extractor just in case it breaks. A replacement extractor for the P365 only costs $8.58 anyway.

In this day and age, if a pivoting extractor is damaged by releasing the slide onto the cartridge, I would call the design pathetic, defective in design and/or materials, and NOT reliable enough to carry. If a pivoting extractor chips, it was excessively hardened, and/or it had a sharp edge that should have been radiused, and/or made from substandard materials.

Some people may disagree, but if one manufacturer can make a pistol that can be reliably loaded by direct chambering, they all can.

When the 1911 was designed there were serious material constraints which affected the way in which it was designed. It's design also added constraints upon how the weapon could be used. But those constraints in materials no longer exist. There is no good reason that any modern pistol with a pivoting extractor should not be able to tolerate direct chambering.

Explain how the manufacturer’s interests, in this case, wouldn’t align with the gun owner’s.

The manufacturer may simply be overcautious and recommend that you NOT do something that is perfectly acceptable.

Or they may tell you not to do something because they KNOW it will break and reveal a design flaw that they don't want you to know about.

It’s not like direct chamber loading is dangerous—it’s not going to incur any sort of liability on their part.

Actually, that isn't true. A customer could make a claim that it is a reasonable expectation that if the pistol allows you to directly chamber a round, the extractor should not fail when the slide is closed. The manufacturer could be looking at a class action claim because of defects resulting from a defective and/or poor design.

You can easily find instances of people chipping/breaking their extractors by direct chamber loading their Glocks.

It the extractors on modern Glocks are chipping, then the alloy was excessively hardened, and/or it had a sharp edge that should have been radiused, and/or was made from substandard materials. If Glock didn't foresee that someone might directly load the chamber, their engineers were very shortsighted. If Glock extractors are breaking from direct chambering, then Glock has a design problem that they need to address.

.....In fact, a common issue with direct-chamber loading in pistols not designed for it is a chipped or broken extractor. Even in modern pistols.........

If a pivoting extractor on a modern pistol is chipping, then the alloy was excessively hardened and/or had a sharp edge that was not properly radiused, and/or was made from an inadequate material or process. That also means that it might fail in normal use. That is not acceptable with the technology of today.

You just made a great argument to go through the analysis that I've outlined to help determine any limitations and/or potential reliability problems of your pistol. If you go through the procedure in the order that I've outlined AND the extractor chips or breaks, then you need to seriously question the reliability of that pistol.

Glock, as does SIG, provides a detailed, step-by-step process they recommend for loading the gun. They don’t list all the possible ways to load the gun that aren’t recommended.

From a liability standpoint that is INCREDIBLY stupid! As a manufacturer you should ALWAYS CYA and specifically recommend AGAINST anything that may cause a failure and/or dangerous condition. If you at least tell people they they should NOT do something because it may cause a failure, then you have less liability in the courtroom.

As an example of a company NOT acting in your best interest, Apple has told many people with dead I-Phones that their stored information is NOT recoverable. When in fact a relatively simple repair could get the phone operating well enough to recover the data on the phone. They also don't want to allow you to use ANY aftermarket parts and in some cases designed their software to NOT allow some aftermarket parts to work in their equipment if it isn't Apple branded. John Deere also does some of this same monopolistic crap.

I think that a longer cartridge is more likely to setback and to setback further per chambering, because the bullet tip will contact the feed ramp sooner before the cartridge is more optimally aligned with the chamber, which will increase the chambering friction, which will likely increase the amount of setback.

The comment you’re addressing is discussing longer bullets (projectiles), not longer cartridges, and the effect of setback (pressure increase) not the likelihood of setback.

Longer bullets are extremely likely to result in longer cartridges resulting in greater setback, hence the relation to your comment.

Some people may think that I'm being way to critical. However, I've spent most of my career working as an engineering technician working in product development labs. I have performed extensive testing using the most extreme conditions to detect design flaws, and would often develop the solution to those flaws. I would not only test for performance compliance, but also for reliability, safety, and regulatory requirements. I have also redesigned problematic equipment already in production.

95% of the time the problems were caused by incompetence, and/or a completely lack of foresight, and/or pennywise dollar foolish decisions, and the problems should never have occurred. From my personal experience, problems that a manufacturer could not have foreseen are rare. I don't cut engineers or manufacturers very much slack when they didn't do their due diligence. I've also had companies ask me to do some very unethical things, such as falsifying safety testing data, which I refused to do.