Comments on: AR-15 Bolt Sheds Lugs — Can You Figure Out What Happened?

By: Hannibal

Hannibal — Sun, 30 Nov 2025 22:35:56 +0000

Two things are true: the bolt is obviously some type of sintered or cast metal, NOT high quality steel as would be expected to be found here. 2. The only way for this to happen is direct & powerful thrust against the lugs while still (at least partially) locked in battery. Assuming number 1. is not the ONLY cause, (nor a super-high-pressure or incorrectly chambered ammunition. Assuming the problem is with the gun & not the ammo, this means the issue was a failure-to-unlock scenario) then the issue was a misalignment of the bolt, due to an undersized cam pin, torqued lower receiver, misaligned barrel extension/locking pin, or incorrectly aligned locking lugs. Somehow the rotational force was negated.

By: C M M

C M M — Mon, 01 Apr 2024 09:59:49 +0000

Looks like a pressure test on the lugs of a bolt.
How much can the lugs take before they give way.
Looks to clean to be a field failure.

By: Bstick

Bstick — Thu, 04 Feb 2021 08:12:56 +0000

I wish there was a way to upload the photo of the brass which was the result of a catastrophic failer brought on by firing my bolt with all but 1 lug sheared off. That 1 lug is definitely gone now. Upper sustained notable damage, dust cover destroyed as was the surefire 60rnd stick mag being used at the time. But this brass…… ive never seen anything remote close to this kind of damage. The back pressure literally imploded the empty brass on itself. Kinda scary. Very scary actually.

By: J Minder

J Minder — Mon, 16 Nov 2020 19:17:25 +0000

First shot squib load. Second shot this…

By: Dave

Dave — Tue, 27 Nov 2018 03:21:05 +0000

Failed cam pin resulting in bolt not disengaging from barrel extension

By: David Biles

David Biles — Sat, 20 Jan 2018 19:47:21 +0000

Improper Headspace

By: Steve Day

Steve Day — Sun, 30 Jul 2017 17:18:40 +0000

I don’t know why some commentors are saying an SAE and Metric “mix-up” happened… The bolt is an AR-15 – There is no Metric version. Only a single standard!

I really hope those guys don’t work on guns. (◔_◔)

By: Terry

Terry — Sat, 18 Mar 2017 05:34:05 +0000

I think it had a round or two that was reloaded too many times and the primer pocket got weak over time. When fired, the shell casing went back and sheared of the lugs.

By: Jimmy

Jimmy — Sat, 05 Nov 2016 07:03:10 +0000

5.56 in a .223 chambered rifle
Over-pressure

By: Phil

Phil — Sat, 15 Oct 2016 01:31:50 +0000

That bolt was probably used in a parted out built weapon. The builder used various components purchased and manufactured from various places, likely. In doing so, he/she simply overlooked the lug spacing requirements, e.g. metric vs SAE. Those lugs likely failed due to not being matched to the barrel lug spacing. If that is correct, the lugs will indeed rotate, but will in turn be about 40% engaged.