6.5 Grendel AR15 bolt failure

[animator]

First time I’ve had a bolt failure in an AR15. I know bolt failure is not that unrare in a 6.5g AR.

This one had about 1300 rounds of almost entirely hand-loads through it. I noticed a significant impact shift, and heard something rattling around in the magazine, and that broken piece dumped out.

Guess I’ll be ordering a new one and maybe one for a spare to keep on hand for the future.

 

[Roc Doc]

First time I’ve had a bolt failure in an AR15. I know bolt failure is not that unrare in a 6.5g AR.

This one had about 1300 rounds of almost entirely hand-loads through it. I noticed a significant impact shift, and heard something rattling around in the magazine, and that broken piece dumped out.

Guess I’ll be ordering a new one and maybe one for a spare to keep on hand for the future.

I keep a spare in my range pack for my 6ARC, same bolt, same potential issue. I consider it a wear item. JP bolts are considered top quality from what I've read.

 

[Stuck]

So whats the general consensus for the cause if its not an uncommon failure? Too much bang for the ar15 sized bolt? I have run an ar10 6.5cm without issue for the last bunch of years with >5k rounds on it so Im assuming it has to be the smaller bolt for a similar output caliber.

 

[Ranch Hand]

It'll be fine, just run it. That's why they put so many lugs on 'em.

 

[animator]

So whats the general consensus for the cause if its not an uncommon failure? Too much bang for the ar15 sized bolt? I have run an ar10 6.5cm without issue for the last bunch of years with >5k rounds on it so Im assuming it has to be the smaller bolt for a similar output caliber.

It’s not so much the caliber, but the case size. The bolt is pretty thin, and when you remove one side of supporting material for the extractor, you get a weak point. The lugs on either side of the extractor are the weakest, and lend themselves to failure in my opinion.

My loads are pretty tame (mid 2400s) so it’s not like I’m hotroding it the way some do.

 

[Roc Doc]

This is a comparrison of a 7.62 x vs. 5.56 bolt. Same with Grendel or ARC, just not enough meat.

 

[Stuck]

Makes sense. I havent played with any of the larger case sizes for sholdered case calibers

 

[Steve300xcw]

Interesting. I have a PSA 6.5 grendel that's around 1500 rounds down range. Makes me wonder if I shouldn't order up a few spares?

 

[aron82]

What make on the bolt?
My 6.5 grendels run odin works bags.
Would probably be a good idea to have a spare or two.

 

[animator]

What make on the bolt?
My 6.5 grendels run odin works bags.
Would probably be a good idea to have a spare or two.

It’s either an Odin or a Faxon. I’ve got a Faxon barrel and Odin bolt carrier, and don’t remember which one I got the actual bolt from.

 

[Aisin]

This is what happens when your barrel isn’t broken in.

 

[78bronco460]

This is a comparrison of a 7.62 x vs. 5.56 bolt. Same with Grendel or ARC, just not enough meat.

458S bolt has the same thin areas but 20k psi less bang on it.

 

[Stuck]

Youd think you could fatten up the wall thickness and make the lugs a little more low profile.

 

[Roc Doc]

458S bolt has the same thin areas but 20k psi less bang on it.

Yeah, 6ARC is limited to 52kpsi, but of course there are guys out there pushing it past spec. I'm completely happy with the 2589fps I'm getting with Berger 105's. At 1k it has the same drop as my 147 6.5CM loads, those little 6mm bullets are damn efficient.

 

[Ebs]

And then, 308 AR bolt vs AR15 7.62 bolt

 

[Aisin]

The CMMG Mutant in 7.62x39 uses an AR10 bolt/carrier to make up for this.

 

[aron82]

$99 for a new bolt from Odin works, or $149 for the entire BCG.
That's kind of annoying.

You don't really need all those lugs do you?

 

[Roc Doc]

The CMMG Mutant in 7.62x39 uses an AR10 bolt/carrier to make up for this.

Interesting, hadn't seen that before, but it's proprietary to that one cartridge, right?

 

[Aisin]

Interesting, hadn't seen that before, but it's proprietary to that one cartridge, right?

I believe so. Do not quote me on that though.

 

[kf4zht]

I got a maxim bolt for mine, $75 - Complete 6.5 Grendel Bolt

They came recommended well on the forums. Website is 10 years out of date but they shipped same day I ordered

 

[CDA 455 II]

First time I’ve had a bolt failure in an AR15. I know bolt failure is not that unrare in a 6.5g AR.

This one had about 1300 rounds of almost entirely hand-loads through it. I noticed a significant impact shift, and heard something rattling around in the magazine, and that broken piece dumped out.

Guess I’ll be ordering a new one and maybe one for a spare to keep on hand for the future.

Ouch

 

[[486]]

I've seen some AR bolts got the extractor-opposite lug cut back to even out the bolt loading so the ones next to the extractor don't want to pop off as often

they still doing that?

 

[animator]

If they are, I can’t easily tell just by looking at it. They all seem to be the same. Haven’t actually measured the lugs.

New bolt is from Odin.