Does anyone have firsthand experience or witnessed a pistol "exploding" due to over-pressure from bullet setback caused by the cartridge being repeatedly cycled through the pistol. I have heard of the possibility but only from the someone said type of urban ledgend reporting. I realize that this could, in theory, happen but wonder how high the probability of this happening with factory ammo. Thanks in advance for your help.
I have not had it happen but am very carefull with it. It IS real a lot of people have no clue about it. It can really be a problem with .40
Based on the response I am begining to think the danger is more theoretical than actual. I am not saying it can't happen or that we should not be aware of the possibility but that the likelihood of this happening with factory ammo is very slight.
In a defensive-strength pistol cartridge, a setback of 1/8" can be dangerous. Not "will be," but "can be."
It depends upon the gun, the powder charge, and the empty space left in the case after powder and bullet are in place.
If you unload daily to practice (which you should, you know), you might try not to chamber the same round over and over again, when you load back up. Every so often, you might check the rounds in your magazine for length against new, unused rounds.
Pistols with smooth feed ramps and smooth chambers, feeding from magazines with properly adjusted feed lips, should not have much of a problem with frequent-chambering setback.
Maybe that would have been a better question, how much setback is dangerous. I don't reload so I thought maybe it could be dangerous in the 100ths of an inch setback. 1/8th inch is fairly obvious I would think that I would see that.
Originally Posted by M1911A1
As I said, it depends upon the gun, the powder charge, and the empty space left in the case after powder and bullet are in place.
Originally Posted by bbqgrill
In a well-packed case, 1/100" setback might cause a very dangerous situation. In a case with lots of empty space, 1/8" may be tolerable.
Maybe the better answer is: Only feed a cartridge from magazine to chamber twice. After that, fire it off in practice. Don't feed it through again.
I think this overpressure/setback issue is more pronounced and seen more in the 40S&W caliber than any other for some reason. I think one website mentions a tenth of an inch setback can almost double the pressures of that cartridge. More so than any other cartridge for some reason.
The Gun Zone -- Glock kB! FAQ Endnotes v1.35
I have a .40 cal that was redesigned from a 9mm. It is the same size as the original 9mm, meaning the barrel is the same outside diameter. This gives the barrel about a 1/2 mm less thickness to work with. The cartridge is also unsupported right at the fee ramp.
Originally Posted by Ram Rod
I believe their are a number of makes of .40 that were designed this way, and that could be source of the perceived problem.
The forum for my gun warns about bullet setback, and points to a couple of the members KBs as a possible consequence.
It depends on the gun, some are more prone to setback than others, from all the threads I have read on this GLOCK's seem to be at the top of that list, but that could just be because of how many there out in service. I use a HK and with their system it is drop the round in the MT chamber, drop the slide, hit the decocker, and I have measured the rounds and have never had one set back yet, and I do weekly tear downs on my CCW gun.
Colt Factory 1911s and their barrels are quite strong.
Colt 1911 firearms/barrels were historically "proof" tested with double charged cartridges.
One Gun Test article that I remember reading was using military surplus Steel .45acp cases and hand-loading them to near .44 Magnum pressures and velocity.
The only modification to the pistol being a much heavier recoil spring.
The testing was not without its problems.
The Steel cases would expand very tightly to the barrel chamber walls and then would refuse to shrink back slightly like typical brass cartridge cases do. They would stick fast in the barrel chamber.
So the extractor heads were getting torn off attempting to extract the steel cases.
That problem was finally solved by lubing the cartridge case exteriors.
Anyway...my point being that the Colt barrel, slide, & steel frame suffered no ill effects even from such powerful and abnormally HOT hand-loads.
The standard brass .45acp cartridge case has comparatively weak and thin walls.
A cartridge of too high intensity and pressure will bulge or rupture the cartridge case during extraction.
Some COLT 1911s have had the grip panels blown off and the magazines blown out the mag well but, the pistols themselves usually remain unscathed and not damaged.
Other non Colt clones may or not be as inherently strong as the factory Colt pistols so I cannot speak for them as I am a Colt guy.
I will have to see if I can find it, but my old Speer reloading manual had the figures for a 9mm with the bullet seated .050 too deep. As I recall it was a significant increase. I think a significant part of it is what is the total volume of the case, and how much of it is actually taken up by the powder charge.
Well, after two weeks no one has said they have witnessed a K/B from setback. We all agree that in theory it could happen but from this thread I have to conclude in the real world it takes extreme circumstances. I don't reload so even though I have two .40 cal Glocks G27 and G22 I am not at any significant risk.
I have personally seen a .40 Glock 35 explode due to setback from a reload with a poor crimp. The other gunsmith I work with was firing it, he wasn't injured seriously but did get some burns and a good whack in the hand. We checked numerous other rounds from that batch of reloads and many had poor crimps and loose bullets.
He's a member here, Pileofbrass. I'll try to get him to post his feelings on it first-hand. You could PM him, but he's usually only on here at work.