best signs of "overpressure"

I'm new to this forum so I hope I'm allowed a few stupid questions till I get on top of things. Here's one, candidate: I've read some strategies for optimizing powder loads for a given rifle/bullet/powder combination. I'm reasonably sure that how to tell if the load is lighter than it should be, however, how do you tell if it's too hot? At the extreme, rifle damage, sure. But what are the reliable indicators short of that? If your grouping doesn't tighten up and you're at the typical maximum load for the bullet, stop there? --or is there anything to be gained by pushing a bit farther? When do you know you've passed any optimal accuracy peak or plateau? What are the signs if, say, your grouping is still improving but your load is exceeding maximum recommended. Any experienced suggestions here will be helpful. Thanks in advance.

 

I keep a close check for primer flattening as one of the first signs myself.

 

The best single indicator of excessive pressure is higher than "book" muzzle velocities.

Primer flattening is not a reliable indicator. Some primers flatten more than others. I did an experiment once, where I loaded cartridges to progressively higher loads. After firing, I popped the primers out and, under a microscope, arranged the primers in ascending order of flatness. There was no correlation between primer flatness and the pressure the cartridge had experienced.

Heavy bolt lift and brass flow into the ejector relief tend to kick in around 70 KPSI. Primers fall out around 80 KPSI.

Miking the case head or the pressure ring is an extremely coarse, almost useless approach. To get either method to work decently, you have to average an unrealistically large sample.

Not to be contrary, but case head separation is not normally a pressure sign. Case head separation comes from the brass being "worked" too much, and the shoulder set back too much/too often. You'll get this especially often if your chamber is a bit on the long side.

 

Primers are an unreliable medium of evaluation.

I found funnies examining primers. I lubricate the 308 and 30-06 ammunition used in my M1a’s and Garands. This practice extends case life. Examining the primers on my fired lubed ammunition, I found they were round. Primers on dry cases were flat. Since everything was the same it seemed unreasonable to conclude that lubricant on the outside of a case could lower the combustion pressures on the inside. I also consider the converse to be true: that is lubricant on the outside of a brass case does not raise the combustion pressures inside.

I figured out that with dry cases the primers backed out to the bolt face on ignition, but pressures were holding the dry case to the chamber walls until the internal pressures exceeded the tensile strength of the brass, causing the case sidewalls to stretch. Once the case stretched back to the bolt face the primer was stuffed muffing like into the pocket. Even medium loads showed flattened primers, and it was a false indication of pressure.

On lubricated cases, the whole case and firing primer slide back to the bolt face, the primer was not muffin stuffed back into the pocket, and the primers for medium loads had rounded edges.

Since this discovery I lubricate my cases during load development and watch for the transition between rounded and flattened primers. This is an indication that pressures are rising but it is not an indication of a maximum load.

Proof positive of maximum loads are leaking primers, pierced primers, and sticking extraction. If I see these indications I consider the load over maximum.

Pierced primers are not also a positive indication of pressure as some primer brands pierce at lower pressures than others. In 1999 Winchester redesigned their primer line, changing the good old nickel plated primer to a brass finish. They also made their primers more sensitive, and they pierce at loads which never bothered the good old nickel plated primers. I ate up a handful of AR15 firing pins using brass finish WSR, and decided never to use that primer ever again. I would experience a couple of pierced primers every ten rapid fire rounds with the things. Last Camp Perry I shot Highpower with a .223, I used the old nickel plated WSR I had, same loads, hot as heck days, not one pierced primer.

Primer pocket expansion is a 100% positive indication of too high of pressures for the case. If your primer pockets expand in 2, 3, or 5 reloads to the extent that primers won’t stay in the pockets, then pressures are very high, even if you are not experiencing leaky or pierced primers. For my long range ammunition, I push the stuff fast and accept a shorter case life as long as I don’t have leaking primers or pierced primers. My short range brass, the loads are mild to mid range, the stuff will last at least 20 reloads if I want to take it that far.

Sticking extraction is a 100% indication of too high of pressures for that mechanism.

The rear locking Lee Enfield is an example of a mechanism which stretches so much that loads which are safe in a 303 Brit Ruger #1 would be positively dangerous in a Lee Enfield. Lee Enfields are extremely flexible and case breakage would occur if pressures were too high for the mechanism. Case breakage is a major reason why the rear locking mechanisms are not encountered anymore in military mechanisms. They stretch too much, the FAL was the last. The case simply stretches too much in these rear lockers and once in a while, a case head separates. I really don't know if you could say it was all due to pressure, but in those mechanisms, if you experience case breakage, I would cut my loads first, then figure out my cartridge headspace.

In any incident of sticking extraction in any mechanism, you must assume pressures are too high.

 

My 300 Win Mag flattens all primers no matter where I'm at on the loading spectrum. Always has, and apparently, always will. Doesn't matter brand of brass or primer, or powder type or charge.

Cratered primers, on the other hand, are my first sign there.

I've never gone BEYOND that point so don't have any first hand experience.

Handguns, I watch for flattened primers, cratered primers, and bulged casings. I've only hit the bulged casing mark when shooting lead out of an H&K USP, something I later learned was a no-no as I spent a couple of hours trying to scrub the lead out of the barrel.

Case head separation can also occur on largish rifle brass that is at end-of-life (on number of reloads), and has been full length sized each iteration. Just something else to watch for - the "bright ring" that forms close to the head is about your only warning there.

Correct me if I'm wrong, but case head separation is not as great of a concern if you are only neck sizing for bolt actions, correct?

 

In response to #5, isn't lubricating cases flipping dangerous? You NEED the brass to temporarily stretch and adhere to the cavity to avoid putting a great deal of stress on the bolt and locking lugs!!!!

The British used to (and may still) PROOF their rifles with heavily lubricated casings.

Everything I know about the mechanics of firearms is screaming out that lubricating cases before shooting them is a BAD idea.

 

Pg 39 Lyman 47th Reloading Handbook:
"Step Six - Lube Removal and Secondary Inspection"
... "Carefully wipe away all traces of lubricant from each case using a clean cloth"...

Pg 163 Sierra V Edition Rifle and Handgun Reloading Data

"Final Inspection/Record Keeping"
... "All traces of lubricant must be removed if this was not done after resizing"..

The actual reference to British proofing their loads there, with a stern caution AGAINST lubricating ammunition, was found in Sierra IV Edition (which contained a heck of a lot more robust section on Reloading, than V edition). I do not have that book handy to cite from, but I remember specifically reading this in that book.

 

Pg 132 Sierra V Edition

"Regardless of which method or type of lube is used, all traces of the lubricant must be removed from the case before firing. Failure to do so will result in raising pressures and bolt thrust to potentially dangerous levels."

Emphasis added.

You REALLY shouldn't be lubing cases when you shoot.

If you want "slicker extraction" try nickle coated cases, those are smoother and will cycle better.

But the lube is bad.

 

Sounds like someone is channeling Col Townsend Whelen and General Hatcher.

These gentlemen actively participated in the 1921 tin can ammunition cover up.

If you recall, in 1921 the Army coated their bullets with tin. To reduce fouling. Also, 99% of the rifles on the line were the single heat treat M1903's, which were dangerous at any speed.

Tin has an affinity for brass, it is called cold soldering. The tin coating on the bullet migrated into the brass case necks effectively welding the bullet to the case. This caused a major bore obstruction.

Instead of admitting that their ammunition was at fault, the Army decided to shift the blame to the shooters. At the time shooters had been greasing their bullets for decades, to reduce fouling. The Army ran rigged tests, “proved” the problem was all due to the grease, and banned greased bullets.

The Swiss Army, being an independent sovereignty, not under the jurisdiction of the American Ordnance Department, used greased bullets in their rifles until the 70’s.



Townsend Whelen was the Col in charge of ammunition manufacture in 1921. As a man who made a very visible mistake, but would not admit it, both he and Hatcher spent the rest of their lives supporting their old Ordnance Department claim that greased bullets were dangerous, Townsend Whelen also adding that oil on cases was dangerous.

The basic question to ask, is what load is the mechanism designed to withstand?

Speer did not provide that number did they? Nor did they provide any indication of how much pressures are raised with lubricated cases. They are simply repeating Hatcher and Townsend Whelen.

I suspect the British lubricate their cases in proof tests to remove the parasitic losses in thrust that occurs with dry cases. A lubricated case will give a truer indication of the cartridge thrust and the load capability of the action.

Given that American manufacturer’s are interested in profit, not the pursuit of knowledge for knowledge’s sake, American proof practice is with a dry case. Oiling cartridges is time consuming, messy and requires cleaning equipment for people and equipment. Dry cases are faster, cheaper, and are good enough for a proof test. And if you want more pressure, you just pour more powder in the case.

You do know that the cartridge case stretches, but you are considering it as a structural load carrying member. It is not a structural member. While the case head of a 308 may lock in and hold up to 25 K psia, at pressures above that the sidewalls yield. Cases are first and foremost gas seals. They must be supported or they will rupture.

Does Speer’s statement conflict with gas lubrication? I think so. Roller bolt mechanisms use gas lubrication to float the upper 2/3rd’s of a case off the chamber walls, to reduce cartridge case friction.




Do you know that 22LR cases are totally covered in wax? Which melts and acts as a lubricant?

And it is there for a reason?

What about Chin’s statements on high power blowback actions?



This was from an Army report on the stresses on steel artillery cases



The best analysis on the web is from Varmit Al.

The bottom line is, too much powder results in too high of pressures, dry cases or lubricated cases. If you are concerned about pressures, cut your loads.

If you are using lubricated cases, such as I, you should set up your sizing dies with a cartridge case headspace gage to ensure that cartridge headspace is within "go" and "no -go". Excessive case headspace will result in action peening, I have no doubt that case lubrication would aggravate action peening, but it will be there dry or lubed cases for cases with excessive headspace.

 

There are none!

If primers don't flatten on 65k psi cartridges why would you expect to see the same primer flatten when loaded in a 50k psi round?

Stay within published data and pay attention to what your chrony tells you

posted via tapatalk using android.

 

Slamfire1 -

Excellent post. Read the study on Varmint Al's page a while back. Seems the trick is to get just the right amount of lube on the case. What and how much do you use to lube your cases?

 

Slamfire;

Thanks for the detailed explanation! That's quite a lot to digest.

I've always treated Reloading manuals as a sort of bible; a long list of Do's and Don'ts that I've committed to memory. My view has been is that it's better to read what to avoid, and do so, than to learn what to avoid the hard way (through accidents).

I know blowback actions require lubrication; I have to use special caution when cleaning 5.7x28mm brass so that I do NOT to remove or damage the dry film lubricant on the cases.

Gas operated systems and bolt action, I just don't understand why one would want to lubricate, given that the firearms are already designed to function properly, and reliably, without it.

The "higher pressure" argument presented in Sierra's book is presented without justification - one point which you made above, which I never noticed previously. Given that pressure is a function of a specific amount of powder burning at a specific rate within a specific volume (with an intricate reciprocity at work between pressure and burn rate), unless the volume was decreased, the pressure would NOT go up. Certainly MORE powder cannot be added during the reaction, nor is there any additional source of heat to speed the burn rate.

Their statement is essentially, if the force is allowed to travel back harder against the bolt face, it would somehow cause the pressure to go up, makes absolutely no sense.

This being said, if you reduce the friction of the casing during the burn process, there is an argument to be made about that case stressing the locking components of the bolt / lugs harder.

However, I cannot think of ANY quantifiable means to measure such an increase in force, if indeed it exists. Without them presenting empirical data of some sort, with hard measurements, their statement moves out of the realm of fact, to that of speculation or assumption. It simply doesn't pass the scientific method test, and is an opinion.

Conversely, I don't see any way to disprove their statement, which is also problematic. Does it cause the locking mechanism to receive a higher force impulse? It may, or may not. It'd take someone with far superior mechanical engineering skills and measuring equipment than I possess, to prove conclusively one way or the other.

Without a pressing need (no direct benefit) for me, I don't see any compelling reason to start lubricating cases just in case they're right about the force aspect. Even though one aspect of their argument can be ruled out as contrary to physics (higher pressure), the second aspect of their argument cannot be so easily ruled out.

Anyway, it was a well presented argument, and I appreciate the time you took to dispel a myth (or all of one and perhaps the other half as well?!).

 

The key that Slamfire mentioned was that the cases should be sized to between 'go' and 'no-go' lengths.

The same principle is used when fireforming, Jam the bullet into the lands to hold the cartridge against the boltface.

 

I started reloading way back when chronographs were not affordable so had to rely on other means of evaluating pressure. I read a lot but not all of the above so forgive me if any of this is repetitious:

1. In my opinion, primer appearance can be a reliable way of determining pressure as long as you understand that the appearance may be different in different guns and different cartridges.

2. In working up some loads, primer appearance is not useful at all. That would include guns not as strong as bolt actions, revolvers, etc. where you will damage your gun long before you see primer signs of pressures. For these you had better stick scrupulously to your loading manual.

3. Signs of high pressure vary in different guns. For instance, as pressure increases, cases on my 458 SOCOM start having scuff marks on the body of the case while with my SKS, there are scuff marks on the case and the rifle starts throwing ejected cases in a different location.

4. I know some of you are absolutely wild about using velocity as a pressure sign. There was a test done some time ago on, as I recall, around 10 "identical" rifles. Muzzle velocities with "the same" load varied by about 200 fps. There are fast barrels and there are slow barrels. In my opinion, muzzle velocity is one of the least dependable so called pressure signs. Remember that published muzzle velocities in may cases were obtained from longer pressure barrels.

 

http://www.shootersforum.com/handloading-procedures-practices/58763-pressure-signs.html

 

Get yaself a venier caliper & measure the case heads .

Start with new cases & measure before & after firing.

Brass moves at what pressures ?????

Primers can be misleading , Blown primers can indicate casehead expasion.

Loose primers ????

 

I watch the diference in primer flatness when comparing it to the same bullet,same powder,and fired in the same gun but as my charge is stepped up.If I start out at 5.0gr of powder X that I know is a mild charge,I note if the primer has flattened,then when I go to 5.5gr,I compare.The to 5.8gr,compare to both previous loads,ect....Untill I get to where I dicide to stop.Most times you can see the prssure rising and tell when the limit is nearing.I wouldn't relie on it to push the boundries or as fool froof, but it does tend to be an indicator worth watching.
Didn't the Japanese have a luber on their machine guns in WWII that lubed the rounds as they fed into the chambers,and if they ran out of lube the gun could blow up?

 

Flattened primers DO NOT indicate "over pressure". Unless they are cratered, punctured or sooty on the perimeter of the primer.

 

Great experience dump... much appreciated

Seems there's a lot of controversy here yet. however, you folks provided me some very important perspective that I don't know how else I would have picked up short of living to 300 years old and destroying an untold number of rifles in the process. This is exactly what I need. As I get deeper into this and learn more about it, there will be more detail oreinted questions. This is a great start, beyond expectations. I joined the right forum, apparently.

Take home reality check are these points I think: use the manuals published by verifiable sources; Examine your brass after firning: any unusual deformation, unusual scratches, separation, loose primers, etc.), use fresh brass for baseline measurements to compare fired brass to, (still not sure about case lubrication, but I'm using a bolt action Tikka, so I'm thinking I should be ok with none for the time being-- need more education here, tho.) Nothing, not even chronys can be relied to to give you a complete picture of overpressure, given all this--bullets sticking in the chamber after firing is a pretty good indicator of overpressure or something like it.

Thanks again for the info. I've downloaded this thread to my ballistic notes binder as a reference. Thanks all for your input--much appreciated.

 

I always check to be sure there's no bolt sticking out of my nose.

Best way to tell that there's no overpressure.

 

One last thought.. don't ever get "casual" about reloading.

There's nothing "casual" about this hobby.

I'm not saying stress yourself out to the point of an ulcer.

I'm saying don't get complacent, that's when accidents happen.

(Same applies to motorcycles).

Vigilance and thoroughness are key - you can never read or learn too much! I've been doing this 15 years, some guys on here 2x or even 3x that long. We are ALL still learning things on a regular basis.

 

Which is good advice and best practice. Unfortunately certain myths and legends get into the public culture, we accept them, and don’t even question why.

I had no idea the association of carrots and rabbits was a spoof of Clark Gable eating carrots in front of Claudette Colbert:

http://www.cracked.com/article_19527_5-ridiculous-animal-myths-that-you-probably-believe.html

The standing of Hatcher and Whelen were so high that no contemporary would dare challenge what they were saying. Even today people treat them as infallible Gods. Hatcher is the master of misdirection. Carefully read the lubricated bullet section in Hatcher’s Notebook. By word play and arrangement of facts, he manages to turn around a situation that is clearly the fault of the Ordnance Department, into one where the blame lands squarely on the civilians.

He also did that with the workers who did the forging of the single heat treat receivers. The problems with the single heat treat receivers were all the fault of the forgers, Army management was totally blameless, victims actually. Poor Army management, cowering in their offices afraid of the militant workers in the forge shop.

Notice when you read Hatcher, nothing, and I mean nothing, is ever the fault of the Army. Bad civilians, bad forgers, Good Army.


We know that whatever tests that Hatcher menitions in his book could not be true, or the Swiss would have had pressure problems for decades. I believe Col Whelen’s subordinates gave him the results he needed to blame shift the incident onto the civilian shooters and their grease pots.

The independence of testers is critical. When they are not independent, the results are always biased in favor of who is providing them their paychecks.

I think it is clear that the 1921 Tin Can ammo coverup is part of the DNA of the shooting community. No one questions it, it is accepted as fact, and it has been built on.

Dick Culver has written historical fiction on the Tin Can ammunition. Entertaining story, all built on a lie. This stuff gets repeated, amplified, accepted as fact, lies become the fabric, foundation, of a culture, a society.

http://www.odcmp.org/1101/can.pdf

There were a number of very successful weapons that used oilers. Oilers were used from 1900 up to 1945.

This Japanese Nambu, that is an oiler on top.









Take a look at this web page. The Schwarlose used oilers.

http://www.gotavapen.se/gota/artiklar/utv_ksp58/ksp14/schwarzlose.htm

It actually took decades to eliminate oilers from automatic weapons. The Germans got the idea of flutes from the Russians, and bingo, no oilers needed.

The use of oilers has disappeared from living memory. But they were there.

I am using case lubrication on my Garand cases and M1a cases to extend case life. I got the idea from a Distinguished HM who found by leaving the RCBS case lube on his cases, he could take a set of cases an entire shooting season.

I took on set of LC 308 cases 22 reloads without a single case head separation.

I don’t like the greasy feel of RCBS case lube. If you drop one of those cases on the ground it collects dirt. When I have time I apply Johnson’s Paste wax with my fingers and buff the cases with a rag. This is very time consuming. But the wax works well and does not attract dirt.

Shot this group, prone with a sling, in a 100 yard reduced match, with my Garand and waxed cases. The cases were on their fourth reload. Shoots fine.



When I have had a quick turn around, I left the RCBS case lube on, trimmed, primed, dumped the powder, and shot the stuff.

Shot RCBS lubricated cases in a Garand Match. Shoots well in a rack grade Garand at 200 yards.



Certain mechanisms, the Garand and M1a are particularly hard on brass. It is “rule of thumb” not to take M1a brass more than five reloads. It is because the mechanism unlocks when there is residual pressure in the barrel and cases get stretched something severe.

These are not 308 cases but the internals of these sectioned cases look like what a dry 308 case would look like after five reloads in a M1a.

I would not be lubing my cases if 308 and 30-06 cases were cheap and lasted forever. It all comes down to cost for me. I want to extend the lifetime of my cases. I want to save money.

 

Leaving lube on cases intended to be fired in modern dry chambers is never a good suggestion, and can likely lead to firearm damage or worse. Case sieze is a necessary event in nearly all firearms, and without it lugs and bolt faces can be set back. This is not a therory or opinion, but a fact supported by all firearm manufacturer's, and is noted in my reloading books as well. What may have been a method of long ago for a vintage WW-I or WW-II weapon doesn't work for modern weapons.

 

Do you have any data which to share?

Is it better than Varmit Al's structural analysis?

http://www.varmintal.net/a243z.htm


If you are worried about lug and bolt face set back, cut your loads. The amount of load reduction you get with case friction is inconsequential to the excessive pressures created by hot loads.

Does a dry film lubricant count, on a modern weapon? Can you get any more modern than the 5.7 X 28 mm case?

http://en.wikipedia.org/wiki/FN_5.7×28mm

FN's 5.7×28mm cartridge cases are covered with a special polymer coating for easier extraction with the PS90 carbine due to the high chamber pressures and lack of case tapering.[32] In addition, this coating ensures proper feeding and function in the magazines.