*Why* Do Some Mfgers Make Their Chambers So Short?

[otisrush]

Earlier I posted about (and people helped me with) some rounds that weren't chambering in my 9mm Walther PPQ M2. (I was able to get rounds to work when I seated the bullet deeper.) Today I received a 9mm case gauge.

The rounds that are not successfully plunking in the PPQ barrel are passing the case gauge test. After doing some searching of previous threads on THR I'm concluding this is not an unheard of situation: Rounds that do fit in a case gauge sometimes do not fit in a particular barrel. (BTW - a sized shell - sans bullet - fits in the barrel just fine.

What I don't understand is how/why this happens. Doesn't this tell me - at least in theory - that I could buy commercially made ammo that wouldn't fit the PPQ? (I know there are situations where certain guns like certain ammo. But I've always taken that to be from a power/cycling-the-action perspective - not actual fit in the chamber. I don't think I've EVER had a situation where commercial ammo I bought didn't fit in a gun I had. Yet this situation - where a round would successfully plunk in a case gauge but not fit in a particular gun - tells me that commercial ammo might not fit some guns.)

What am I not understanding here? I would think the spec is the spec. And if the case gauge matches the spec - then gun manufacturers' guns should accommodate within the spec. I know different bullets can have different profiles, etc. etc. But the bottom line is this: It passes the case gauge plunk test but fails the PPQ plunk test.

Any enlightenment I would gladly take.

Thanks.

OR

 

[rcmodel]

The case gage is likely cut to see if the case will chamber.

It is not intended to cover every bullet profile, and every chamber leade ever cut in a gun barrel.

The other thing is, many if not most European handguns are chambered for FMJ military ammo.

And they are made to European C.I.P chamber specs.

Not American SAAMI specs.

Bad situation, but that's the way it is when the guns people buy are made all over the world anymore.

rc

 

[Clint M]

Also note this is not your problem but barrel twist rates differ in rifles, a fast twist 1/7 223 rem will need a much longer throat than a 1/14 twist because the extra bullet weight makes the bullet longer being the diameter is constrained to .224..

 

[rcmodel]

Actually it doesn't.

No matter the .223/5.56 bullet weight, or length?

It has to be 2.260" long or less to fit in the magazine.

Longer or heavier bullets just seat deeper in the case to maintain the max OAL that will fit in the magazine, or feed system in the case of belt fed machine-guns.

rc

 

[Clint M]

Maybe 223 was a bad cartridge to choose, I was thinking more in terms of BR type guns and the change from old 222 rem to ppc, and 6br etc then to heavy bullets and fast twist where a dedicated throat was cut, I don't know why I tried to connect the two.... that's what I get for staying up past my bedtime...

However I do know they allow single shot (not constrained to magazine length) on one event of shooting AR's using the heaver bullets, so I'm still unsure, and not wanting to look up specs this late LOL... I will just submit to your wisdom, and post count

 

[higgite]

Like RC said, cases gauges are just that, case gauges. Although, the ones I've had also indicate if the cartridge exceeds SAAMI max OAL or not, they aren't sensitive to bullet profiles. Your cartridge may well "plunk" in the case gauge and may even be shorter than the gauge but still be way too long for your pistol. Similar to how your empty cases plunked okay in your pistol but your loaded cartridges were too long in the other thread that you mentioned. The reason they can be too long for your pistol and still plunk okay in the gauge is the gauge doesn't have lands for the bullet to run into.

 

[Conservidave]

In this situation, your PPQ is your case guage it seems. Frustrating i know because my XDS had the same issue. I am almost certain the chamber was out of spec, but she's gone now.......

 

[Sam1911]

I know different bullets can have different profiles, etc. etc. But the bottom line is this: It passes the case gauge plunk test but fails the PPQ plunk test.

You've answered it for yourself! As rc said, many makers build gun barrels to fit military FMJ 9mm NATO ammo, period. They really don't take into account that you might use a chubby 147 gr. truncated cone bullet, or a bulbous 124 gm. "small ball" slug or whatever else that will touch the leade before the case is fully seated against the shoulder.

That's why the "plunk" test was invented. Using the barrel you have, check the ammo you want to use. If it plunks in and drops out cleanly, you're in the clear. If it doesn't, you'll need to seat deeper (which is no problem) or use a different style of ammo if you're buying factory stuff.

 

[otisrush]

I think I need to make my question more focused and specific.

I know that different reloaded rounds may fit in one gun and not another. I know that differences in chamber lengths / where rifling begins (I think that's the part that can be variable) can impact what fits and what does not. So that for reloaded rounds, as a result, bullet profile and COL play a big part in whether a given reload will work in a given gun. And a round might work in gun A but not in gun B. I understand all that. It's frustrating - but I get it.

This is what I don't get: Why do we NEVER see this variability of cartridge fit from gun A to gun B when we use purchased ammo? Do the ammo manufacturers, essentially, design their cartridges (bullet profile and COL) and then plunk it in all kinds of guns? When I buy any ammo I don't even WONDER if it will fit in my guns - any of my guns. So clearly the manufacturers are making it in a way that fits virtually all guns. Are they designing to a spec that is guaranteed to work in all? And if that is the case - then it seems there is an opp to have a "chambering gauge" for us reloaders. LOL

OR

 

[Sam1911]

Well, of course a manufacturer spends the necessary effort to make sure the combination of cartridge components they use will fit 99.999% of guns out there. That means they're minimum spec. They can't afford to field 37 phone calls a week from gun owners that had jams with their ammo. That also means that their ammo isn't really perfect for any one gun. I might like to load as long as possible for one gun, but accept that it won't fit another gun. An ammo manufacturer will not put themselves in that position because they're in the business of selling as much ammo as they can to as many shooters as possible.

And yet, sure, there are times when gun "A" just doesn't like ammo "B". I've run into factory ammo that stuck hard in the leade of one gun or another. Not common, but it happens.

 

[otisrush]

Well, of course a manufacturer spends the necessary effort to make sure the combination of cartridge components they use will fit 99.999% of guns out there. That means they're minimum spec.

Clearly they do.

Does a minimum spec exist? Or do they basically need to actually test it in tons of guns?

 

[Blue68f100]

Some times a gun goes out the factory door without the leads/chamber having the final cut. It could have been a worn tool head that caused it. In most cases contacting the factory for a return will get it fixed. With most all gunsmith fit barrels the chamber needs to be reamed after fit. Most drop end barrels are machined deep enough it's all most impossible to have this problem. Most any GS can run a finish reamer into the chamber and correct the problem.

 

[Sam1911]

Does a minimum spec exist? Or do they basically need to actually test it in tons of guns?

Sure. There are SAMMI and C.I.P. drawings for the cartridge, including the bullet curvature. But again, unless you're looking to fire THAT NATO spec bullet, the drawing doesn't much help.

The thing is, though, they don't have to test it in every gun out there. Or even every kind of gun. Most of us could tell you a list of guns known to have short leades and if it works in them, it will work in anything.

(I'd go with CZs and xDs, myself.)

 

[egd]

What I never could understand about your oal problems was (if I remember from the other threads correctly-big if ) that factory ammo fit just fine and it's usually around 1.150 or so, but your loads at about 1.135 or so did not fit and you had to go down to around 1.10 before they would fit. Is that correct, roughly? If so, it still makes me think that something about the way your dies made that intermediate length round caused some kind of a bulge or something that was just enough to cause the problem, but not enough to visually see. Otherwise, like you say, it just doesn't make sense.

 

[Sam1911]

egd, it's much simpler than that.

The curve of the leading edge of one bullet doesn't necessarily look just like the curve of another. Some are straighter and taper to the nose more sharply, some are curved right from the case mouth, closer to a triangle shape.

If the gap before the start of the rifling is cut short, that "fat" part of the bullet may hit it and start to poke the bullet into the rifling, causing a jam.

Take a look at this graphic:



Makes it pretty clear.

 

[egd]

OK, Sam, your drawing makes it a lot more understandable. Therefore the factory bullets are probably all shaped more like those in the bottom,green, drawing so they will fit in most all guns. While his bullets were probably shaped more like the top drawing, he had to keep going down in length til he got clearance.
Since he has had all this trouble and other PPQ owners don't seem to have this same degree of trouble, do you think maybe his gun is out of spec or something and should be sent back to be checked out?

 

[otisrush]

The round on the left is the factory round that fits. The round on the right is my reload that fits - the one with the short COL.

I'm of the belief after all of this that the Zero Bullets 124gr has a profile that brings out the short chambering issues of the PPQ.

Just by eyeing it the different profiles are pretty dramatic.

OR

 

[higgite]

egd, it's even simpler than that. In the OP's other thread he said he was using Zero bullets. The ones I have used have a shorter, "fatter" profile than a lot of others. Even though the bullets are shorter, they hit the lands higher up on the ogive than other bullets, requiring a shorter OAL. I have to seat Zero 124 gr FMJ-RN (the OP's exact bullet if I recall) at 1.110" or shorter for my CZ, but I can (but don't) seat Remington 124 gr FMJ-RN out beyond SAAMI max OAL and they will still plunk okay in the same pistol.

Edit: OP posted while I was typing. His pic illustrates the situation perfectly.

 

[egd]

Yep, just like Sam's drawing.
Now , if we could just solve the rest of the worlds problems.....

 

[Sam1911]

do you think maybe his gun is out of spec or something and should be sent back to be checked out?

Most likely not. Just needs to either find factory ammo using the NATO spec bullet profile (most does) or load his own rounds a hair shorter and test them to find out what length works.

 

[mdi]

Overthinking this. OAL is the method of measuring the depth of the seated bullet from case head to bullet nose. What it does not measure is the distance from the case head to the ogive of the bullet, i.e.; the full bullet diameter, which will determine how far into the chamber the round can enter. In Sam's drawing, the bullets are the same, the OAL is the same, but the difference is the leade. Your gun obviously has a "shorter leade". No big deal, just determine your OAL for your particular bullet by how it fits the chamber. As mentioned above. factory ammo is made to fit as many guns as possible...

 

[Edarnold]

If you examine factory loads using the 115gr or 124gr Hornaday XTP bullets, you'll see that the bullets are seated very deep, with just the very edge of the cylindrical portion peeking out the case. The result is a short COAL, which is echoed by the recommended seating in the Hornaday manual. With a correct leade, that same bullet can be seated to 1.142", which gives you a considerable increase in case capacity, allowing less anemic ballistics at normal pressures. I hit it lucky, the Walther P1 and HK P7 that are my 9mms both accept a full length loading with these bullets, which means I can take advantage of loadings that develop considerably better ballistics.

Were it my gun, I would have a competent pistol smith ream that leade until it accepted properly loaded ammo.

 

[Sam1911]

Sure. You could do that if you want to load to the ragged edge. (With your IMproperly loaded ammo! Lol.)

Hey, while you're at it, have him ream it to 9x21, or 9x23!

The guns work the way they were intended to. If you want them to work differently from their intended spec, you'll have to change them.

 

[LiveLife]

The round on the left is the factory round that fits. The round on the right is my reload that fits - the one with the short COL.
I'm of the belief after all of this that the Zero Bullets 124gr has a profile that brings out the short chambering issues of the PPQ.

Looks that way. If you look at the picture below of Winchester 115 gr FMJ loaded to 1.135", you can see longer, more slender nose profile than Zero bullet. I have found that not all FMJ/RN have the same nose profile (ogive) and will require different lengths to work properly in different barrels, especially in barrels with shorter leade/freebore (look at picture below of MBC SmallBall with shorter rounder nose compared to Dardas/ZCast stepped RN with longer more pointed nose for another example).

 

[LiveLife]

Were it my gun, I would have a competent pistol smith ream that leade until it accepted properly loaded ammo.

Sure. You could do that if you want to load to the ragged edge. (With your IMproperly loaded ammo! Lol.)

Hey, while you're at it, have him ream it to 9x21, or 9x23!

I am with Sam1911 on this one. I don't think the OP or any other PPQ owners need to ream out their barrel. As already illustrated by the OP, I think proper component selection is the resolution.

I use KKM and Lone Wolf 40-9 conversion barrels for my Glocks and while KKM has longer leade/freebore, Lone Wolf barrels were reamed at the factory that allows longer than SAAMI max of 1.169" OAL/COL of most FMJ/RN profile bullets. But the latest Lone Wolf barrel for G23 has very short leade (like my Sig 1911 barrel with almost no leade). While MBC RN (SmallBall) would work with KKM/LW barrels at 1.080"-1.100", the new LW barrel would not work as OAL that passed the barrel would severely compress the powder charge.

I was a bit disappointed as I really liked MBC RN but found my solution with Dardas/ZCast RN bullets with "steps" that allowed longer 1.125" OAL with "steps" preventing bullet shoulders/bearing surface from hitting the start of rifling and bullet seating depth that did not compress the powder charge.

You could ask why not just go with KKM barrel with longer leade/freebore? Like Sig 1911 barrel, the shorter leade reduces high pressure gas leakage around the bullet and seems to produce greater accuracy. With that said, KKM has slower 1:20 barrel twist rate (compared to 1:16 for LW) which IMO is more compatible with lead/plated bullets for accuracy so if I was shooting matches with G23, I may go with KKM barrel instead and load my rounds longer.

In this comparison thread, I range tested jacketed/plated/lead bullets with KKM/LW barrels and KKM barrel produced slightly greater accuracy with lead/plated bullets - http://www.thehighroad.org/showthread.php?t=745656