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Posted: 2/1/2012 1:49:35 PM EDT
| When I carry my pistol I always load in a round and when I get home I take it out and put it back in the mag. So it gets rechambered quite a bit. I'm going to start measuring over all length to make sure it doesn't go to deep. This is factory Gold Dot ammo in a .40. How much set back would be unsafe? Thanks guys. |
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Good question.
Any set back is bad, but I can't answer the question of how much set back is too much. The internal volume of the case decreases rapidly as the bullet seats deeper. An autoloader cartridge doesn't have a firm crimp to hold the bullet, say as we would use on a .44 Magnum, so pushing out of the crimp can't be used as a guide. I think the safe approach is to cycle different cartridges through the chamber every day, and be vigilant for set back. Or use a revolver! 
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Quoted:
Good question. Any set back is bad, but I can't answer the question of how much set back is too much. The internal volume of the case decreases rapidly as the bullet seats deeper. An autoloader cartridge doesn't have a firm crimp to hold the bullet, say as we would use on a .44 Magnum, so pushing out of the crimp can't be used as a guide. I think the safe approach is to cycle different cartridges through the chamber every day, and be vigilant for set back. Or use a revolver!
Are you saying rotate all the rounds in the mag so they always alternate? I'm going to take one round and cycle it 50 times and see if any set back occurs. |
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40 S&W is already a high pressure round, and the effects of bullet setback is magnified relative to lower pressure calibers (45 ACP, for example).
I would see if I could pull the bullet a bit with a collet -type puller. Barring that, discarding it is the safe thing to do. |
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Quoted:
What I meant was unload the magazine, then reload so the first round into the magazine is rotated to a different cartridged periodically. Set back is a common complaint and some people have a habit of rotating the cartridge that is chambered every day. Will do. Thanks a lot for your help! |
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Pressure can go through the roof if the bullet setback is severe. How much setback? It all depends on the weight of the bullet, the powder, the volume remaining, etc.
I've had it happen with XTP's and Golden Sabers the worst. The Saber has a short driving band leaving the rest of the ogive slack with the case. What I do you may not be able to do. I simply don't unload my duty gun except for cleaning. I open up the safe, carefully draw the pistol and set it on it's shelf in the safe and lock the door. I almost never have a setback cartridge now. I have on occasion put a cartridge with a setback bullet and slightly pull the bullet with a hammer type bullet puller, reseat the bullet to the correct depth and taper crimp. Haven't done this in YEARS but I have done it with my .45 ACP hollow points. That's a cheapskate thing to do and of course I'd just shoot that bullet up on the range and never carry it on duty again to trust that crimp job. Simply not worth it. |
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A year or so back, SIG and Glock put out memos to LEO and the like, cautioning against the officer unchambering the same round at the end of the day and then feeding it back into the chamber via the magazine. The officers tended (tend?) to do this on a daily basis and that round is subjected to a fair amount of set back and then KBing, or at least they were (are) 'more prone' to KBing.
Rotate the rounds and after X amount of cycles through the batch, rotate them out and get fresh ammo. I guess one could drop that particular round into the chamber and offset any set back, but I don't know if this is the correct watch to go about the problem. Chris |
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Setback of more than a few thousandths (more than 0.005") can become problematic or even dangerous depending on the cartridge and load.
Personally I try not to load/unload the same round often, so once I chamber a round in my carry gun, I leave it there until I have to unload it (or when I go to practice, I just fire it). |
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I've read about this for years, so a quick search brought up lots of info....the top one on the search screen is "thegunzone.com" who is pretty good at giving sources of his info.....even Wikipedia had the following (with sources):
Writer Walt Rauch who first brought forth information that bullet set-back such as often occurs in administrative unloading/loading) in the .40 S&W could raise pressures exponentially. Rauch published some specific information on this set-back issue in the May/June 2004 Police and Security News, in a feature entitled Why Guns Blow Up! "The simple chambering and rechambering of a cartridge does push the bullet back into its case."
Hirtenberg Ammunition Company of Austria (at the request of GLOCK, Inc.) determined that, with a .40 caliber cartridge, pushing the bullet back into the case 1/10 of an inch doubled the chamber pressure. This is higher than a proof load. This can occur with but one chambering since it is dependent on how well the case was crimped or sealed to the bullet. If only .1" doubles pressure then pressure rise per 1/32" is something to be concerned about. I think the best practice (in addition to emptying the magazine and changing the order in it) is to practice with what you carry. Shoot the stuff before it has time to work its way back....and learn how to maximize case/bullet friction in your taper crimped bullets. There is also the compatibility issue that arises with particular bullets and crimp dies.....for example, Remington Golden Sabers and Lee Factory Crimp Dies. The method of crimp that works for most other brands of bullets can easily crush the jacket of a Golden saber in such a way that it actually can make it looser. There is a lot of banter about it on the web, debunkers, and supporters of this notion. But I read the information on Lees site and Remingtons site a few years ago, where Remington warned reloaders not to use FCD's on their bullets, and Richard Lee countered with, in effect, then use better bullets. (there was an obvious rift for a while.  ) I can't find the comments on either site any longer so perhaps Remington changed their design a bit.........its one of those things that doesn't make much press when a reconciliation is effected....and/or tempers cool off...either way the effect is the same....bury it.
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Quoted:
Why the empty chamber when you get home? Quoted:
Setback of more than a few thousandths (more than 0.005") can become problematic or even dangerous depending on the cartridge and load. Personally I try not to load/unload the same round often, so once I chamber a round in my carry gun, I leave it there until I have to unload it (or when I go to practice, I just fire it). I guess I will just keep it loaded till I have to unload it. |
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