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Old January 3, 2020, 05:23 AM   #1
JJ45
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How many times can you chamber a round safely?

I have been shooting for a long time but have never given a thought to how many times I can eject a round from an auto loading pistol then re-chamber it safely.

The concern is that the bullet may "set back" which might increase chamber pressure when fired.

Talking specifically factory loads, .45 ACP chambers at the case mouth and there is no crimp groove so I assume the factories use a taper crimp. Not sure if bullet movement caused by ejecting and re-chambering the round would be more likely with certain cartridges such as 9mm, etc.

Should I worry about it? Thanks for any advice...JJ
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Old January 3, 2020, 07:33 AM   #2
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Just to clarify, you're asking about ejecting a live round(unfired) and then reloading and rechambering the ejected round? Personally I'd be more concerned about the rim of the cartridge, and the dirt the round would collect wherever it lands. I'm sure the impact of the round hitting the ground enough times isnt good for the case/crimp/bullet in general.
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Old January 3, 2020, 07:37 AM   #3
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It really depends on the shape and crimping of the cartridge. Some. like 40S&W are more prone to bullet setback than most tapered cartridges.

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Old January 3, 2020, 08:35 AM   #4
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I've rechambered 9mm defensive ammunition that has a cannelure multiple times without noticeable setback. As someone mentioned above, the case rim gets chewed up and I typically replace the round because of that.

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Old January 3, 2020, 11:15 AM   #5
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There are far too many factors to allow giving a definitive answer. It depends on the shape of the bullet, how tightly the ammo maker crimped the rounds, how cleanly the particular firearm feeds the round into the chamber, and possibly others. I carry 1911s. Bullet setback is a known issue with 1911s in general, so I try to rechamber the same round as infrequently as possible. Toward that intent, when I unload my carry pistol I usually rotate the round that comes out of the chamber down toward the bottom of the magazine when I load up again.
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Old January 3, 2020, 01:46 PM   #6
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What he ^ said.

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Old January 3, 2020, 02:57 PM   #7
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I've done the chambered round in the magazine rotation before. The end result in my experience is every round in the magazine might get varying degrees of setback. I'd rather monitor one round than all of them. Personal choice.

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Old January 3, 2020, 03:11 PM   #8
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There are far too many factors to allow giving a definitive answer.
I can give one definitive answer, and that is that bullet setback is not a "must/will always happen thing.

Seems to be a more common thing today, though I don't know if that is because of certain pistols being more common, the internet making us more aware, or if ammo makers are not making ammo exactly the way they used to. I suspect a bit of all of them.

However, I have seen factory .45ACP ammo bought in 1980, chambered so many times over 20+ years that the nickel cases had brass stripes worn on them. Literally hundreds if not thousands of chamberings, all from the magazine. The bullets (measured often) never moved at all. The ammo was fired in 2000 and functioned flawlessly, exactly has it had when brand new.

SO, despite the fact that it does happen sometimes, its clear to me that it doesn't HAVE to happen, so someone simply isn't making the round to stand up the way they could be.
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Old January 3, 2020, 05:14 PM   #9
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Depends on bullet, crimp, feedramp and other factors.

I tend to also rotate the chambered bullet and if it's been chambered a few times or I have concerns I just grab the calipers and check the overall length.

To date I've only had setback once, with Remington GS and my 9mm 1911, specifically the 10 round mags for my CCO. Since the top round seems to ram into the front of the mag when manually trying to remove (without a tool, good luck!) them by hand I'm not surprised.

I've got a few well used and many times chambered 230 grain HST in a box I've checked a few times but no movement from the Glocks or 1911s (damaged rims seems more prevalent in well used HST). I think it's a combination of good crimping and a full case for HST.
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Old January 3, 2020, 07:05 PM   #10
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Old January 4, 2020, 02:33 AM   #11
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My Carried ammunition does not need to worry about whether it will be damaged from cycling in and out of the chamber because that is the first ammo shot and replaced with new as often as I can. With an active shooting program worn cartridge cases or set back bullets are just not a problem. Then there is the shooter who will buy one box of twenty specialty rounds and carry them forever because another box would be cost prohibitive to purchase. Ammunition carried in a defensive firearm should be shot in training exercises on a regular basis to insure smooth operation and reliability of the pistol.
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Old January 4, 2020, 05:14 AM   #12
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Some premium defensive ammunition has a case cannelure to help prevent setback.
.45 acp Hydra Shoks for one.
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Old January 4, 2020, 06:09 AM   #13
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Depends on the gun and the ammo.

At one point I found a recommendation by one ammo-maker that stated they felt their premium self-defense ammo should tolerate being chambered 4 times before it began to setback.

But that doesn't mean all ammo will handle that. I've found some budget practice ammo that would set back noticeably from being chambered just once.

Some loadings are more touchy about setback than others. Where you're most likely to get into trouble is with short cases and heavy bullets. In other words, when there's not much space behind the bullet in the case to begin with. When the round doesn't have much space in the cartridge behind the bullet, even a relatively small amount of setback can result in a large relative decrease in volume and that's when things can get dangerous.
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Old January 4, 2020, 11:11 AM   #14
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While not factory ammo, I have a few powderless, primerless rounds (.45 ACP, taper crimp) that I use for function tests and reloading practice that have been chambered dozens of times, and one of them suddenly showed signs of setback, in conjunction with damage to the bullet.
Prior to that, no obvious scratches or marks on the case or bullet.
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Old January 4, 2020, 12:10 PM   #15
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Try a test run

Take your pistol and remove the slide. Leave barrel in receiver in the position the round would feed. Insert a magazine with round into the receiver. See how much of your round will hit anything. Next take your rounds to your kinetic bullet puller. How much effort is needed to pull the bullet. Next ask yourself what did you find about "set back." Personally, I'd look for ammo problems before attacking the handgun. Next I'd look for a messed up magazine. Take a decent handload or factory round to see how hard it is to pull. I'm skeptical. Never been able to get set back.

Added: For that matter, take your handgun, unloaded, and slowly let the slide forward. See the relationship between slide, barrel and feed ramp. I did this with a Glock, HK and a 1911. See what that bullet nose hits. Also, push hard on the bullet down on a hard surface. See what happens.
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Old January 4, 2020, 03:26 PM   #16
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Depends on the cartridge and whether it has a crimp at the cannelure. One thing that I do know for sure is that most 357 Sig rounds can't be rechambered more than a few times before there is obvious bullet setback.
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Old January 4, 2020, 05:50 PM   #17
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357 SIG----Not So
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Old January 4, 2020, 08:41 PM   #18
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The real danger of set back is not so much higher pressures, although that IS a problem.
The problem came to be known as "Second round stoppage" and it caused some stoppages in actual police shootouts, some of which were caught on squad car cameras.
The cop could be seen firing a first shot then his pistol would jam.

In the early days of the police move to the auto pistol they had a rash of situations where the gun would fire the first round, then fail to properly feed the second round, causing a jam.

This was traced to the police pistol inspection process.
People would remove the mag and clear the chamber for inspection, then insert the mag, chamber the round, then put the first round back in the magazine.
This meant that the same two rounds were being chambered over and over, pushing the bullets back into the case.
The stoppages were caused by rounds that had too short an overall length and would miss-feed.

To fix the problem police were trained to not chamber the same rounds more then a couple of times, and ammo makers began making ammo for police use that were made to allow more chamberings without excessive set back.
Most police ammo makers warrant the ammo for 3 to 4 trips into the chamber before it should be fired in practice or discarded.

To help eliminate problems, some people take a factory fresh round out of a new box of ammo and store it.
Then, they use the factory fresh round as a "gauge" to check for bullet set back in the ammo that's in use.
When you see the bullets beginning to move into the case, stop using it and shoot it in practice.
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Old January 4, 2020, 10:35 PM   #19
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Set Back: Sorry, could not make it happen in my G23.4 in 357 SIG factory OEM barrel installed. Second Round Stoppage also has to do with the way magazines are loaded. Has to do with tension of top most cartridge causing a malfunction. You will find it is problematic in a Glock to not to feed out of a magazine. I will be glad to load up some rounds and give it a try at the range. I will say these problems are outside my experience.

Looks like in this litigious world the larger ammo companies would put out a warning. Could I have missed this warning?
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Old January 5, 2020, 12:15 AM   #20
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I take the attitude that if it gets ejected without without firing, it’s a done round.
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Old January 5, 2020, 02:31 AM   #21
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Quote:
Looks like in this litigious world the larger ammo companies would put out a warning. Could I have missed this warning?
I don't think you missed it. I think the ammo makers are taking the safe legal route by simply not saying anything about it.

In a way its like firearms makers, being under no compulsion to make guns that allow fired cases to be reloaded. The responsibility is to for the ammo to work, ONCE. After that, you're on your own.
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Old January 5, 2020, 05:41 AM   #22
J.G. Terry
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The big question is what does the round hit to set the bullet back. Take one of these rounds and push down on it as hard as you can. See how much you can set it back. I think this set back stuff is a creature of the net.

Added: We may have gone as far as we can go on this one. This look like the dog chasing its tail.
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Old January 5, 2020, 10:37 AM   #23
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It depends on the cartridge. Some are more prone to setback than others and obviously higher pressure cartridges will in turn gain more dramatic pressure spikes than lower pressure cartridges.

Generally speaking, it takes some MAJOR setback to exceed the margins for safety and typically setback of that magnitude will cause feeding issues far before they reach that point.
So if the cartridge has visible setback and will no longer chamber reliably, that's your cue to remove it from circulation.

The dramatic effects of setback causing catastrophic case blowouts are highly exaggerated and built on outdated circumstantial evidence such as Gen 1 .40cal Glocks KABOOMS, ignoring the fact that Gen 1 .40cal Glocks had a completely unsupported chamber, thus making cases more prone to bulging or blowing out.
No firearm with a fully supported chamber would ever have such issues firing factory loaded or otherwise responsibly handloaded SAAMI Spec ammunition, but sensationalism prevails so it became a runaway cautionary tale in which the ultra-high-pressure .40 S&W cartridge (which in reality has equal pressure to a Standard Pressure 9mm Luger) when chambered once or twice converts a pistol into a hand grenade.

That being said, a simple way to prevent setback is to avoid unnecessarily clearing your firearm on a daily basis.
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Old January 5, 2020, 01:59 PM   #24
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I usually get a dozen or so before the bullet gets some setback. I typically carry 9mm. I think I get fewer out of my 45s typically. depends on your definitition of safely, and the gun doing the chambering.
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Old January 5, 2020, 07:55 PM   #25
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Set back cause

In another forum the cause of set back was explained. The way this happens is the round is picked from the magazine by the slide at high speed. This sudden acceleration cases the bullet to set back into the case. That is the cause of set-back

Added: The Second Shot Failure had to do with a full magazine. The top round in the full magazine would press on the bottom of the slide. This pressure would cause the Second Shot Failure.
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