ammunition, gun-safetyThe scenario where this happens most is when I have to unload a firearm to take it to the range. It is generally loaded and chambered when at home, and when I re-load the firearm, sometimes the round that was previously chambered will end up being chambered again.
I have heard criticism of this practice, and would like to hear solid information as to the real concern here.
I have never experienced a significant problem, but you should pay attention that the over all length (OAL) of the round is not changing. I have seen bullets pushed back into the case on semi-autos that could cause failures or malfunctions.
Also, inspect the rounds that get cycled for significant damage.
When in doubt, throw it out.
Yes. For ammunition that you must rely on, if you have chambered a round once and have to remove it from the chamber, discard it or set it aside for training. If you are not depending on this ammunition to do your job or save your life (home defense, police, military, hunting, etc.) then you are fine with taking the chance of a misfire. For shooting at the range and just for fun there is no issue with rechambering rounds repeatedly.
Repeated chamberings carries the risk of bullet setback, where the bullet is pushed farther back inside the casing. This can cause various problems and should definitely be avoided. If the bullet is lose or you can see a gap between the edge of the casing and the side of the bullet, toss it.
In the AR15 platform, the floating firing pin inside the bolt will repeatedly strike the primer of the round. 5.56mm ammunition uses hard primers so that the light strikes from the firing pin do not cause problems.
The problems arises when the primer is lightly struck repeatedly. The primers will be more and more prone to failure with each strike, even after a very small number of chamberings. A large california SWAT department had two documented issues with this, one a misfire during a raid and one when they went to the range to fire the rest of their ammunition in an attempt to diagnose the problem. Others have had issues as well and I have seen similar things on ranges in the military.
However, despite what appeared to be good primer strikes, two problems were discovered. First, when accurately measured, some of the primer strikes had insufficient firing pin indentations. The failed round from the potential OIS incident had a primer strike of only .013”—the minimum firing pin indent for ignition is .017”. In addition, the primers on the other rounds were discovered to have been damaged from repeated chambering. When the same cartridge is repeatedly chambered in the AR15, the floating firing pin lightly taps the primer; with repeated taps, the primer compound gets crushed, resulting in inadequate ignition characteristics–despite what appears to be a normal firing pin impression.
—5.56mm Duty Loads by Dr. Gary Roberts (aka DocGKR)
Besides the OAL issue you don’t say HOW you are chambering the round, but avoid placing the round directly in the chamber by hand and dropping the slide on it, which forces the extractor to “jump the rim”. This will cause unnecessary wear on the extractor and even outright damage. The preferred method is to insert a magazine, cycle the slide and then remove and top off the mag.
The usual concern I am aware of over this is with rifles with free-floating firing pins, such as the AR15 and AK47. On these types of weapons, when a round is chambered, the firing pin strikes the primer lightly, and can sometimes leave a visible mark. The concern is that if the same round is chambered repeatedly, these repeated light strikes could eventually cause a discharge. I haven’t heard any reports of this happening, but to be on the safe side, I’d avoid rechambering the same round more than a few times - either rotate it out with some other ammo, or fire it off.
This isn’t a concern on handguns, because almost all of them have sprung firing pins and most have firing pin safeties as well.
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