First Bolt Failure

[Bronz]

At the range today working the gun moderately. Really just getting it hot to see if it will hold up in a class.
Only about 80 rds. fired, but the last 60 constant. Not fast as range is a 1 second between shots place.

Rifle. Saber 14.5 upper, withholding the bolt Manf. at this time. Carrier I think it?s a RRA.
Ammo. Wolf 100 gr. Steel case.

I was checking DOPE at 7, 10, 25, 50 and 100. I got the barrel smoking. I haven?t torn the rifle down yet and I will check all the empty cases as I do save them.

I first thought I had a broken extractor, because I saw a case still in the chamber. Closed the bolt a few times trying to get the case out. I started to think my first stuck case. I have never had one, but locking the bolt to the rear the case just slide out.

I looked a little closer and damn, saw a piece of bolt missing. Lug on left side of the extractor is gone.

Once a you lose confidence in a rifle it's hard to get it back.

Can you guys tell me if anybody has had this happen to them and suggestions for bolt replacements.

Thanks.

Will try to post some pics. When I get home.

[grayfox]

Has not happened to me with all the grendels I shot/shoot, but then again I do not get barrels smoking, nor fire 60 constant - sounds like "as close to 1 sec/ea as you could" - nor do I do it with steel case ammo. And as I understand it, the shorter the barrel, the harder the cycling. I personally do not consider the Grendel a blaster-type rifle.

No offense intended but regardless of the bolt or the replacement, you need to examine the operator procedures and operating parameters first.

[A5BLASTER]

I haven't broke one yet. But do keep spares well let's face it it's a part designed to break.

I have run my 16 inch very hard, harder then you were running yours. I have done multiple 28 round mag dumps, had the barrel hot enough I bet I could have lite my cig off of it.

I run adjustable gas and lowmass bcg's plus square the reciver just for this reason. Keeps the bolt lugs locking up square and reduces the gas needed to drive the action and that reduces wear greatly.

I would have to check my log book but I'm north of 5000 rounds now on that barrel and I'm positive 4500 are a lil more of that is wolf ammo.

I would square your reciver and drop in a lowmass bcg and adjustable gas add a new bolt and keep on rocking that bad boy.

[VASCAR2]

Sorry to hear about your bolt and if I needed a replacement 6.5 Grendel bolt I’d use a group buy Monster logo bolt manufactured by Millennium. Other quality bolts are Alexander Arms and Maxim. JP bolts get good reviews.

Two areas of concern which might accelerate bolt wear is a receiver that is not square resulting in the bolt not being square with the barrel extension. If this is a carbine gas 14.5” barrel the upper might be over gassed which can put more stress on the bolt.

Depending on the number of rounds on the bolt might indicate poor heat treat. If the bolt failed on the first 80 rounds of Wolf steel cased ammo I’d suspect a faulty bolt. If the bolt lasted several hundred to thousands of rounds I’d look at contributing causes which lead to bolt failures.

[FRB6.5]

OP out of curiosity what was the ejection pattern like prior to failure?

[Bronz]

Has not happened to me with all the grendels I shot/shoot, but then again I do not get barrels smoking, nor fire 60 constant - sounds like "as close to 1 sec/ea as you could" - nor do I do it with steel case ammo. And as I understand it, the shorter the barrel, the harder the cycling. I personally do not consider the Grendel a blaster-type rifle.

No offense intended but regardless of the bolt or the replacement, you need to examine the operator procedures and operating parameters first.

Not looking for a fight but care to elaborate on your last paragraph.

I was operating the rifle to or what should be under it’s operating parameters. I was literally firing a shot and saying in my head 1 Mississippi and firing another shot. Now, if that questions what you think is outside of an AR platform rifle well that’s your opinion. It shouldn’t be, 60 rds is not that much.

[Bronz]

Sorry to hear about your bolt and if I needed a replacement 6.5 Grendel bolt I’d use a group buy Monster logo bolt manufactured by Millennium. Other quality bolts are Alexander Arms and Maxim. JP bolts get good reviews.

Two areas of concern which might accelerate bolt wear is a receiver that is not square resulting in the bolt not being square with the barrel extension. If this is a carbine gas 14.5” barrel the upper might be over gassed which can put more stress on the bolt.

Depending on the number of rounds on the bolt might indicate poor heat treat. If the bolt failed on the first 80 rounds of Wolf steel cased ammo I’d suspect a faulty bolt. If the bolt lasted several hundred to thousands of rounds I’d look at contributing causes which lead to bolt failures.

I am sure hoping on faulty bolt. It is a part and parts break. I forgot to add. It’s a mid-length gas system and this bolt has probably about 600 to 700 rds on it. Maybe more that sounds low. I will have to check my book.

[Bronz]

I got the gun apart. Will take pics and post if I can figure that out.
Definitely a shears lug and bonus the lug fell out when I got the carrier out.

[Brazz04]

Why withhold the manufacturer's name? Just curious as to what purpose that serves?

[grayfox]

Not looking for a fight but care to elaborate on your last paragraph.

I was operating the rifle to or what should be under it’s operating parameters. I was literally firing a shot and saying in my head 1 Mississippi and firing another shot. Now, if that questions what you think is outside of an AR platform rifle well that’s your opinion. It shouldn’t be, 60 rds is not that much.

Sure I will elaborate. And this is all my own opinion, you can take it for that as input and make your own decisions. I was "brought up" in engineering terms in the US nuclear navy, and a chief principle was, even though we had operating parameters and were designed as a (multi-billion) warship to operate in battle conditions, one of the primary rules was you do not over-stress your equipment beyond what is needed for the job at hand. 2 pumps in slow are better than 1 in fast even though both of those were acceptable operation. Like I said this is just my own point of view.

I would view a 556 or similar AR as more suited to a sustained, rapid fire situation than the Grendel, again, IMO. The Grendel has more bolt cross-sectional area and thrust, and has a thinner face/rim to handle the larger case bottom, these 2 things contribute to a larger thrust and force against the bolt lugs (anyway this is how I understand it) -- this all being said sustain-fire is probably taken into account of somehow in this design, notwithstanding.

The Grrr, however IMO, is more of a select your target and fire for accuracy, not fire for effect or suppressing fire, or other terms that I'm not as familiar with... so this all being said you could be right that it was all inside of AR parameters.... but for my money, if I'm not at war, and not in a rapid-fire-needed situation, I would personally not be inclined to do that type of firing. I probably differ in this viewpoint from others but that's the $0.02 that I would advise.

[Bronz]

First attempt at posting a pic. Lol zero

[Bronz]

Sure I will elaborate. And this is all my own opinion, you can take it for that as input and make your own decisions. I was "brought up" in engineering terms in the US nuclear navy, and a chief principle was, even though we had operating parameters and were designed as a (multi-billion) warship to operate in battle conditions, one of the primary rules was you do not over-stress your equipment beyond what is needed for the job at hand. 2 pumps in slow are better than 1 in fast even though both of those were acceptable operation. Like I said this is just my own point of view.

I would view a 556 or similar AR as more suited to a sustained, rapid fire situation than the Grendel, again, IMO. The Grendel has more bolt cross-sectional area and thrust, and has a thinner face/rim to handle the larger case bottom, these 2 things contribute to a larger thrust and force against the bolt lugs (anyway this is how I understand it) -- this all being said sustain-fire is probably taken into account of somehow in this design, notwithstanding.

The Grrr, however IMO, is more of a select your target and fire for accuracy, not fire for effect or suppressing fire, or other terms that I'm not as familiar with... so this all being said you could be right that it was all inside of AR parameters.... but for my money, if I'm not at war, and not in a rapid-fire-needed situation, I would personally not be inclined to do that type of firing. I probably differ in this viewpoint from others but that's the $0.02 that I would advise.

With that mindset sir why do we have cars with speedometers that go to 200 but we are only supposed to go 55. Now would I fire my match M1a like that no, but an AR should be able to get hot and not fail.
Hopefully it was just a fluke.

I like your signature quote. Best on the forum.

[Keef]

Good Lawd, apparently it's your fault Bronz, you're just not "one shot, one kill" enough for the grrrr. Lol.

[JCSC]

Toolcraft offers lifetime guarantee, or so I thought.

I

[Lemonaid]

https://www.youtube.com/watch?v=BSizVpfqFtw

That wasn't you in the above video was it Bronz?