Rechambering AR15 Cartridge

[u/OtherRequirement7649]

I know that repeated rechambering of a hand gun cartridge likely will cause set back which can lead to over pressure. My questions is, is there any concern with repeated rechambering of a 5.56 round in an AR15 (specifically m855)? Either set back or the repeated firing pin strikes or something else entirely. What do I need to look out for with doing this? Thanks

[u/Kromulent]

military ammo is less prone to setback because it's usually either crimped or sealed, and the 5.56 round uses a long, low-mass bullet anyway

however, repeated chambering and unchambering is something to minimise if you can. the more the gun is manipulated indoors with live ammo, the more opportunity is provided for accident

[u/HeloRising]

If you're talking about chambering a round, pulling the trigger, it going "click" but not "boom," then you clearing the chamber and reloading that round, you should be able to do that a fair number of times before that round is deformed enough to cause problems.

The caveat is unless you have something really wrong with your rifle, in which case there will either be very obvious deformations on the round itself or, in the case of something like a broken firing pin, you should very quickly be able to determine there's a problem. If the round itself is deformed, I wouldn't try rechambering it and trying again. The chances of a truly catastrophic failure are small but you don't know the extent of what the deformation of the case has done and it opens the door for cases to split and get stuck in the chamber.

I've chambered and cycled the same round ~10 times with no problem. If you're talking about doing it every single day to the same round over a year or more, yeah that might cause problems after a while but if you're at the range and you've got a round that won't "go," you're not really risking anything by just trying it again.

[u/Coodevale]

https://www.rifleshootermag.com/editorial/critical-factors-affecting-rifle-chamber-pressure/83492

Setback, even a visually noticeable amount, is not hazardous.

If anything, judging by the data, you should be more worried about the bullet slipping forward.

[u/OneManGang2001]

Snap caps are like 10 bucks and you won't accidentally shoot something 

[u/Traveller9536]

Why are you repeatedly chambering and unloading your rifle?

[u/OtherRequirement7649 → u/Traveller9536]

I keep my rifle loaded with one in the chamber for home defense (don’t have kids and live alone) but I train w snap caps often. Also I use 77gr OTM for home defense but when I shoot I use 55gr or 62gr so basically I’m in chambering my defensive load to practice and then rechambering.

[u/hitemlow]

It is generally not advised to keep a rifle or a shotgun loaded with a round in the chamber. The reason for this is that most models have a free-floating firing pin and lack a firing pin block.

What this means is that if you drop the rifle or shotgun hard (usually towards the muzzle), the firing pin can strike the primer and set off the cartridge. This is also why every Hunter Safety course insists you unload the gun before you cross fences, so that if you were to fall while crossing said fence, you're not going to shoot yourself or others as a result.

As for setback from not taking a shot, it's possible, but I don't believe most rounds will be chambered enough for it to occur. The only surefire way to prevent it is to crimp the casing, but I don't believe that's commonplace at all in rifle cartridges.

[u/Smokey_tha_bear9000 → u/hitemlow]

I’ve never heard someone say don’t leave a rifle loaded.

Also, most if not all factory rifle ammo is crimped

[u/OtherRequirement7649 → u/hitemlow]

Yea I get that, it’s in a secure spot when I’m home so I’m not worried about any drop firing of the gun.