AR-15 Bolt Head = Fail

jester421

jester421

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Now I need A new one :(
 
This is a common failure in the AR 15/M 16 family. It usually happens after approx 10,000 rounds in a Mil Spec bolt and fewer with Non MILSPEC Bolt. There is a DOC from SOCCOM detailing the failure rate.
R711 OUT
 
Commom crack area for DPMS

FOR DECENT BOLTS

5-6k in a carbine

10k plus in a rifle

That said - I have had a Colt bolt go in under 300 rds suppressed...
 
I was gonna toss in my .02 but KB has already put in most of what i was gonna put down.

The other failure point I've seen is bolt lugs. Usually the ones beside the extractor claw.

NS
 
I have several broken mpi bolts along with non mpi. just happens after time. some sooner than later.
If anyone has broken bolts you can send them to me if you don't want them.
 
dangertree said:
MPI (magnetic particle inspection) tells you it wasn't cracked or flawed when it left the factory. It doesn't mean it will last longer.
Click to expand...

Roger that.

The same with the idea on Proof Testing, it effectively takes 1/3rd of the life from the bolt.
Althought it will typically show flawed bolts that would have been missed without.

If you control the steel used in the bolt and manufacture process, you can greatly reduce the need for proof testing.

We do not proof test our Mk11 Mod0, Mod1, Mod2 guns while we do proof test the M110 SASS bolts. Same bolt - different contract (SOCOM versus Big Army) during endurance testing the SASS Proof Round bolts will always fail before the non proofed bolts.

Bill Alexander (Alexander Arms) does not beleive in Proof Testing either.


HOWEVER the catch is most of the manufactuers that proof test and MPI their bolts use the highest quality components. Those who do not go thru the testing, do not.
 
What else is damaged, and how likely is injury to the operator when bolt failure occurs? Do you change out bolts on old guns as prevention?
 
depends on the failure.

Lug failures are quite common when shooting high volumes. No major issues, some just remove the offending lug and keep shooting.
 
I guess this is why "they" say to carry a extra bolt, firing pin,pin retainer and bolt cam in your pistol grip instead of batteries and dubbies ;)
 
KevinB said:
depends on the failure.

Lug failures are quite common when shooting high volumes. No major issues, some just remove the offending lug and keep shooting.
Click to expand...

The first bolt head failure I ever saw was a range-use C7 bolt at Connaught Ranges. It looked funny when I pulled it out of the box to do my share of the after annual qualification clean-up. No way at all of knowing how many rounds it fired. That was the same shoot when the barrel lug broke on the Browning HP beside me. It just jammed solid(!) on the guy.
 
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