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Discussion Starter · #1 ·
I heard someone today say that they never put a round that has already been in the chamber back in the chamber to carry. They set it aside and use it as range ammo. There was no real reason given, I was just wondering if anyone else does that, and or what is the reason?
 

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It's about bullet set back. When a round is chambered the force pushes the bullet back into the caseing. This causes the pressure of the cartidge to rise and if enough set back occures you could have a kaboom insead of a bang when you pull the trigger. This could be bad enough to damage the gun or injure you. That being said set back wont occure after a round is chambered once.

I may rechamber a round 4 to 6 times a month depending upon range trips and cleaning frequency. I always make sure the same round is rechambered so i can keep track of it. At the end of a month I fire that 1 round off and replenish the mag. The round could probably be rechamber more before set back was an issue but this routine it easy to keep track of and only costs 12 rounds per year.

IMO its worth the $5 to $10 a year to insure my gun doesnt go kaboom in my hand. The cost associated with only chambering a round once is not worth is. Thats assumming you can find the ammo to replace it with.
 

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Discussion Starter · #3 ·
It's about bullet set back. When a round is chambered the force pushes the bullet back into the caseing. This causes the pressure of the cartidge to rise and if enough set back occures you could have a kaboom insead of a bang when you pull the trigger. This could be bad enough to damage the gun or injure you. That being said set back wont occure after a round is chambered once.

I may rechamber a round 4 to 6 times a month depending upon range trips and cleaning frequency. I always make sure the same round is rechambered so i can keep track of it. At the end of a month I fire that 1 round off and replenish the mag. The round could probably be rechamber more before set back was an issue but this routine it easy to keep track of and only costs 12 rounds per year.

IMO its worth the $5 to $10 a year to insure my gun doesnt go kaboom in my hand. The cost associated with only chambering a round once is not worth is. Thats assumming you can find the ammo to replace it with.
Wow, I have taken several different "safety" classes and not one has ever mentioned that.

Great information Thank you!
 

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I suspect it's related to this:

Some guns tend to push the bullet deeper into the casing when the round is chambered. Differences of a few 0.001s of an inch in the shape of the chamber or depth of the rifling can cause this. If a bullet is pushed further into the casing, it might be held tighter by the casing crimp. It would then require more pressure to get that bullet moving, which might result in a misfire or other malfunction (bullet stuck in the barrel, failure to fully cycle due to less recoil, etc.). I have read that in extreme cases, the bullet got so jammed in there that its resistance exceeded the rupture strength of the casing, resulting in a catastrophic failure. (Theoretically, guns with chambers that are not fully supported (such as Glocks) would be more vulnerable to this.)

You can check if your gun does this by repeatedly chambering and ejecting the same round, then comparing its overall length to a fresh round (or measure it before and after with a caliper if you have one).

You make yourself most vulnerable to this if you constantly re-insert your ejected round at the top of your magazine. This allows the same round to be loaded/ejected over and over. To avoid this, I'll pop several rounds out and put the ejected round further down in the stack. But I'm not clearing my weapons every day. In situations where you clear your weapon often, it might be easier just to relegate the ejected round to the range bag than to keep track of which rounds have been chambered and which haven't.
 

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Some calibers are more susceptible to round set back. .40 cal. being one of the worse, due to the shape of the bullet (
flat nose vs. round nose). In any case, you can make a quick and inexpensive "Go/No Go" gauge very easily. Take a stiff piece of card stock, with the card stock stood on a flat surface, place a new round beside it. Mark where the nose of the bullet is, then cut the card stock, so the bullet tip touches the notched out area. When you check a bullet, if the tip no longer touches the cardboard cut out, you know you have set back. If it still touches, your good to go.
 

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Some calibers are more susceptible to round set back. .40 cal. being one of the worse, due to the shape of the bullet (
flat nose vs. round nose). In any case, you can make a quick and inexpensive "Go/No Go" gauge very easily. Take a stiff piece of card stock, with the card stock stood on a flat surface, place a new round beside it. Mark where the nose of the bullet is, then cut the card stock, so the bullet tip touches the notched out area. When you check a bullet, if the tip no longer touches the cardboard cut out, you know you have set back. If it still touches, your good to go.
Great info, also add .357 Sig to that category of being setback prone. Both .40 and .357 Sig operate at fairly high pressures for handgun calibers in general and are prone to setback as well. I took a class once where the instructor said something to the effect of "if you chamber a .357 Sig round and don't fire it, throw it away." That's a bit extreme, but I get his point. I like my fingers attached and functional.
 

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You certainly can check the setback, if any, by examining the cartridge with a magnifying glass. The setback will be fairly obvious if it is occurring. As said in previous reply, for the sake of a few cartridges every year and peace of mind, put them aside for range shooting. Then again, if it is good enough to shoot at the range then it would be good enough to use for defense. Personally I will rechamber a few times and examine the cartridge before I rechamber ---if I see no problem, them I use them as I would any other cartridge. The only time this comes up is my home defense firearm that I used to keep chambered---since I use the firearm for target shooting with different target ammo every two weeks, I now just leave the firearm unchambered and just remove the mag and replace with another mag that contains my target ammo, which eliminates my need to worry about any setback.
 

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If I plan to expend the mag (and chambered cartridge) every month, then I should be ok right? As part of my drill, I want to shoot 50 rnds of target ammo followed by 10 rnds of SD ammo every two weeks.
 

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If I plan to expend the mag (and chambered cartridge) every month, then I should be ok right? As part of my drill, I want to shoot 50 rnds of target ammo followed by 10 rnds of SD ammo every two weeks.
At that rate of use I wouldn't be concerned unless it was with a very high pressure cartridge like .357 Sig or a +P+ loading in 9mm. Although .40 is known to also be prone to setback, I don't worry about un and re chambering a round provided within reason. It is a high pressure round, but I don't shoot reloads or hand loads and I have a Glock and an M&P and I know both are tested with proof loads that are MUCH higher than anything likely to be caused by setback.
 

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If I plan to expend the mag (and chambered cartridge) every month, then I should be ok right? As part of my drill, I want to shoot 50 rnds of target ammo followed by 10 rnds of SD ammo every two weeks.
Save the SD ammo for defense. In the future it could be more difficult/expensive to find,hard to believe at current prices. There is no need punch paper with 260 rounds of quality SD ammo a year. Put that cash into more FMJ. Whatever difference there is in recoil between your target and FMJ ammo will be negligiable durring the adrenaline dump of a SD situation.
 

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I just check the OAL of the cartridge with a set af calipers,, If set back bad I take puller & hit a few times,, Check OAL then taper crimp.. Then when I have a mag full I'll shoot at range ; )
H/D
 

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I re-chamber at least once daily (more if I'm doing something like going to a school to get my kids or a post office, when I leave my empty pistol safely behind). I rotate the first two rounds over the course of a week, and rotate between three magazines weekly. About every three months I empty all of my expensive carry ammo at the range, and then rotate to three different magazines. I perform a chamber check each and every time I reload, and forcefully seat the slide / round.

I have been following this routine religiously over the past 16 months that I've been carrying. I have used two types of ammo (first Federal Hydra-Shok JHP, and Hornady Critical Defense for about the past year). I have not had a single issue - not one. So, while there may be extreme cases of something like this happening (they mentioned it once in training, but noted it was someone who used the same round over a year or two) it is likely the exception and not the norm.
 

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I have seen very little setback on my cartridges over the years. However I did have several, 4 to be exact that did not go off and 2 that hang fired about a second after the hammer struck the firing pin. I sent them to the manufacture and they confirmed what I had thought, there primer charge had dislodged from the cup and wasn't able to be set off. This was a result of several years of chambering at random, it happened because I would empty the mags of my defense rounds to shoot IDPA matches, then reload them, I also let the slide close by releasing it, I now follow it down to a closed position.
 

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Seems like the re-loaders would be a bit more worried about setback than those of us who use factory loads. But it still doesn't hurt to rotate them as you swap out the mags between defensive rounds and range ammo.
 

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IMO its worth the $5 to $10 a year to insure my gun doesnt go kaboom in my hand. The cost associated with only chambering a round once is not worth is. Thats assumming you can find the ammo to replace it with.
I don't get it... kaboom as in a little more kick or kaboom as in it blew up your pistol? All that will happen is more pressure will be created, +p or maybe even +p+ but a quality firearm will be ok.

I have never heard of a round with a little setback blowing up a modern firearm!
 

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I don't get it... kaboom as in a little more kick or kaboom as in it blew up your pistol? All that will happen is more pressure will be created, +p or maybe even +p+ but a quality firearm will be ok.

I have never heard of a round with a little setback blowing up a modern firearm!
Do a search, on RARE occasions with EXTREEM set back your gun can blow up in your hand. You would have to re chamber the round more than a couple of times. Still, it is something to be aware of and avoid.
 

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Seems like the re-loaders would be a bit more worried about setback than those of us who use factory loads. But it still doesn't hurt to rotate them as you swap out the mags between defensive rounds and range ammo.
Not so. I did a test rechambering my reloads and some very well-known SD loads and one of the commercial loads setback worse than the reload. The simple solution is to quit playing with a loaded gun; leave it chambered.
 

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Discussion Starter · #20 ·
At that rate of use I wouldn't be concerned unless it was with a very high pressure cartridge like .357 Sig or a +P+ loading in 9mm. Although .40 is known to also be prone to setback, I don't worry about un and re chambering a round provided within reason. It is a high pressure round, but I don't shoot reloads or hand loads and I have a Glock and an M&P and I know both are tested with proof loads that are MUCH higher than anything likely to be caused by setback.
Standard pressure 9mm not an issue, or at least as much of an issue?
 
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