cracked bolt on AR

[vtb]

Hello sh.

Bought new AR. After 920 rounds discovered this:

Question is - should I just replace cracked bolt and go on (like shit happens) or should I perform some deep check of the system?

If yes - what should I check?

Thank you in advance.

 

[rgrmike]

I've seen a bolt carrier group literally break in two pieces. I've seen this a few times too. I'd just replace it and drive on. If it's a rifle that you're betting your life on then by all means give it a very careful check. If not, replace it and don't worry about it. It's a machined part and the reality is sometimes stuff breaks.

 

[BoilerUP]

Brand of AR/BCG?

 

[EL34]

I'm gonna agree with rgrmike, stuff breaks. Buy yourself a quality replacement, and drive on.

 

[ORD]

That is probably THE single most "broken" area for bolts (around the cam pin area...at least for crappy bolts...good ones break much later and usually around the extractor-cut bolt lugs, etc.) that I have seen over the years and not surprisingly so given that is one of the weaker points of the bolt. 5k rounds is roughly the "average" service life of a mil-spec bolt (although I think that the recommended replacement range is ~4k, but some can go for 10k+ and far, FAR more). At only 920 rounds fired, short of a catastrophic f-up of some variety with the weapon, that is a VERY low count for any bolt to break like that, so my money is on a flawed bolt (whether a poor quality material used to make it, poor workmanship, improper heat tx, etc., etc....who knows at this point beyond a pure guess). Out of curiosity though...what specific make/model/etc. rifle/bolt are you dealing with?

If it were mine, I'd opt just to replace it with a quality, Mil-Spec Carpenter 158 steel, shot peened, HPT/MPI tested bolt and chive on.

 

[vtb]

Thank you for replies.
I've already informed maker of the rifle that this issue happened.

And (thanks God) i've bought replacement bolt for "just in case" from Brownells.
But - can you provide an exmaple of "...quality, Mil-Spec Carpenter 158 steel, shot peened, HPT/MPI tested bolt.."?

Thank you in advance

 

[LRRPF52]

I've done the same thing, only at over 10,000 rounds of intense high-volume range sessions on one of my first 3-gun AR15's.

I replaced it with a Colt military bolt.

That is unsat for 920rds. I'll bet you this was an 8620 bolt with improper heat-treat made within the last 24 months, if not the last 12.

8620 with proper heat-treating is fine for the .222 Remington at 50,000 psi, but not the .223 Remington or 5.56 NATO loads at 55,000-62,000 psi.

What ammo were you shooting, what barrel do you have, and what is your chamber? .223 Remington, 5.56 NATO, or .223 Wylde?

Follow ORD's advice and get a Carpenter 158 High Pressure Tested, Magnetic Particle Inspected marked bolt from a reputable source. Most parts suppliers have started carrying them after people began shooting high volume and demand for more than a vismod plinker look-alike AR15 increased.

Bravo Company is one excellent, reputable source for C158 HPT/MPI bolts. So is DD, Spike's, and you will find them at Brownell's, PSA, along with other vendors online.

 

[USGILT]

+2 for BCM; they make a great product.

BCM AR15 Bolt Assembly MPI

 

[bustin]

Hello sh.

Bought new AR. After 920 rounds discovered this:

Question is - should I just replace cracked bolt and go on (like shit happens) or should I perform some deep check of the system?

If yes - what should I check?

Thank you in advance.

That bolt looks melonite treated. Was it advertised as Melonite treeated?
If I were you I would check the ejection angle. If throwing forward of 3 O'clock, add an adjustable gas block to cut down on the gas a little. At the least a heavier buffer or spring or both.

 

[rgrmike]

I've heard great things about BCM. I run Daniel Defense in a few of my guns and haven't had any problems. I have seen some Daniel Defense bolts break though. They were very high round count guns however.

 

[wareagle700]

BCM, Daniel Defense, LMT, pretty much any milspec bolt that is HPT/MPI is GTG. However, no manufacturer is 100%. Stuff breaks, thats why its good to have a few spares.

 

[303_enfield]

That's the part that fails. I have had one USGI issue bolt fail in 25 years, but have seen ten other USGI fail. On the civilian side I have seen dozens fail in the last two years. Lots of cheap bolts on the market. Get a MPI bolt and drive on.

 

[346ci]

The 5.56 and 6.8 superbolts we sell made by AR15 Performance have that area beefed up to help with the issue seen here. They have a .526" band around the cam pin area that most don't. I have a new digi cam on the way and will get some better pics later...

 

[E. Bryant]

I don't see any markings on the bolt indicating MP inspection (maybe they're present but not shown), and the surface finish of the body OD in the vicinity of the cam pin hole leaves much to be desired. I normally wouldn't get too wound up about tooling marks, but man, that's a terrible spot to be leaving a bunch of "crack starter kits".

Buy a new bolt as suggested above and move on. Better yet, buy two so that you have a spare for yourself or a buddy. You may also want to replace your cam pin, and I'd definitely throw it away if there is the slightest sign of wear on the OD.

 

[Tx_Flyboy]

Vtb,

Who made the bolt? and rifle?

also, i did not expect ownership of an AR-15 is legal in Russia?

 

[usmcmk12]

+JP enhanced bolts