Broken bolts- thing of the past?

[shootdr1]

I an newer to the Grend. game so I am sure this is a silly question, but are the broken bolts a thing of the past? I thought they were then I spoke to a smith who I respect and he said he actually still gets a lot of people in with broken bolts. Now, I am not sure on specifics etc.. but I thought that issue was resolved years ago. I have a Satern barrel with the bolt they provided and I do not push hot loads at all. I am debating another Grend. build but I wanted to be sure. Thanks and I am sure this has been addressed a lot! But I cannot find anything new on it.

[LR1955]

I an newer to the Grend. game so I am sure this is a silly question, but are the broken bolts a thing of the past? I thought they were then I spoke to a smith who I respect and he said he actually still gets a lot of people in with broken bolts. Now, I am not sure on specifics etc.. but I thought that issue was resolved years ago. I have a Satern barrel with the bolt they provided and I do not push hot loads at all. I am debating another Grend. build but I wanted to be sure. Thanks and I am sure this has been addressed a lot! But I cannot find anything new on it.

SR1:

I haven't seen a post about broken bolt lugs on the forum for about a year but I am sure they still happen. A lot of places are making Grendel bolts these days and some have bad lots of them or just don't know how to make them so a guy ends up with ones that shear lugs. There is more to it than just the bolt manufacturing process so if you want to learn more about it you can run a search on 'sheared' or 'broken' bolt lugs. LRRP52 is the guy who you ought to look at because he has spelled out the reasons for sheared lugs a couple of times over the years.

If your bolt was made well and you keep the loads within the bounds of published data, your bolt will last a long time. I do not think they last as long as a decent mil spec 5.56 bolt but some guys here have gone over 10K rounds without shearing a lug and that, to me, is remarkable. I have sheared lugs on six bolts over the years but the bolts were made before the newer metallurgy and technology that is used today.

My advice remains for Grendel owners to have a spare bolt handy.

LR55

[A5BLASTER]

I an newer to the Grend. game so I am sure this is a silly question, but are the broken bolts a thing of the past? I thought they were then I spoke to a smith who I respect and he said he actually still gets a lot of people in with broken bolts. Now, I am not sure on specifics etc.. but I thought that issue was resolved years ago. I have a Satern barrel with the bolt they provided and I do not push hot loads at all. I am debating another Grend. build but I wanted to be sure. Thanks and I am sure this has been addressed a lot! But I cannot find anything new on it.

After you said he still she's broken bolts. Did he try to sell you a diffrent chamber or cartridge? If so I wouldn't put much faith in what he told me after that.

Without having more details on the bolts he has seen broken, there really isn't anyway to draw a conclusion from his word.

I have had 6 diffrent grendels 5 ar grendels and a howa grendel.

All of my ar grendels have either used the JP grendel bolt, AA grendel bolt sold by AA or the group buy grendel bolts.

Haven't broke a bolt or extractor yet. The 20 inch I sold not long back had close too 1600 rounds on it when I sold it most of that like close too 1200 rounds was handloads that I can't confirm but feel confident were in the 54 thousand psi range.

Have a 16 inch that has somewhere over 2600 rounds on it, my log book shows 2, 187 of those rounds is wolf, the rest a mixture of factory and handloads.

I pulled down a 200 round case of federal fusion and reworked it up and it is for sure over 52 thousand.

All bolts will break no matter what case they are designed to hold. When you push to far past saami pressure levels. How many rounds you get on it before it breaks depends on how far past you go and a few other factors.

Now the big question is where is that departure line of good bolt life vs pressure.

Meaning if we push to 53 thousand can we expect X count bolt life or if we push to 55 thousands can we expect Y count bolt life.

Nobody can tell use that because nobody has done a study like that.

Square the reciver face, run good ammo, maintenance your weapon and keep a spare bolt on hand and enjoy your rifle.

Nothing, nothing, nothing and I mean not one single part of a ar15 rifle is meant to last your lifetime. Every single part is a consumable part. They are designed to wear out and be replaced.

[BluntForceTrauma]

Thanks, A5, good write-up.

[A5BLASTER]

Thanks, A5, good write-up.

I tryed my best lol.

You know rereading this thread has made me decided too do something.

I'm going to buy a new barrel and jp bolt and work up a load that I can use the quickload app and set it at 55 thousand psi. And see how many rounds it will take too break a bolt.

I will buy 3 bolts and repeat it and see what the data tells us.

That are somebody could bring a bolt out a higher pressure bolt hint hint lol.

[HuntTXhogs]

Maxim firearm bolts are designed for higher pressure than 55k

That’s straight from the horse’s mouth , Frank the operator of the business ...

[VASCAR2]

There are recipes for broken 6.5 Grendel bolts, Satern/Liberty 18” barrels with over size gas ports plus short chambers. Another culprit having a barrel extension not square with the bolt putting uneven pressure on the bolt lugs in combination with hot ammo. Another potential culprit, 18” mid length gas barrel with no adjustable gas block running a suppressor. Another area of concern to me are 6.5 Grendel or variants with .125 bolt face bolts of dubious quality which might be more prone to breakage.


I feel sure if people were regularly breaking bolts we’d see it here on the forum. In my opinion the current 6.5 Grendel bolts are doing better than the 7.62x39.

[Wanderson]

And ARs break bolts, that's just a fact. it's an excellent design but it's one of it's weaknesses. Most AR guys (me included) keep spare bolts.

Fortunately, I've not broken one yet, and I've shot a lot of 7.62x39 thru ARs too. I was lucky enough to start with a good bolt (LMT) and it's been used for two different 16" builds, still going strong. I'm also not one to do lots of mag dumps so I'm not punishing mine like others may do.

And with BCGs getting cheaper (Right To Bear has a Toolcraft nitride 6.5G BCG for $90) there's no reason not to have one on the shelf. or do what I do and build another 6.5G AR. There's no better backup than another rifle.

[A5BLASTER]

Maxim firearm bolts are designed for higher pressure than 55k

That’s straight from the horse’s mouth , Frank the operator of the business ...

Ok just so we can clarify. He said his grendel bolts are designed for more then 55k psi?

And does he have any test data to support the claim.

Not calling BS but I like to see data to support stuff.

[shootdr1]

All great info and that is pretty much I gathered from doing research, but I figured you guys on here would know best. It seems like JP bolts and Maxim may be the way to go for piece of mind. I plan on grabbing spares for sure as well. I always do for all my rifles.

[PredatorDown]

I've got north of 5k rounds through my JP barrel/bolt and have seen no cause for concern. Most of my loads are mid-range pressure wise, but I've also ran some pretty hot loads with 100gr amax. With that being said, I have broken 2 extractors

[A5BLASTER]

I've got north of 5k rounds through my JP barrel/bolt and have seen no cause for concern. Most of my loads are mid-range pressure wise, but I've also ran some pretty hot loads with 100gr amax. With that being said, I have broken 2 extractors

When you say perrty hot loads. Could you give us a reasonable pressure level of those loads.

[centerfire]

Broken bolts are a reality for some people who hand load. I think the cartridge unfairly gets the blame. I'm pretty new to this forum but in the short time I've been here I've seen more than one thread about broken bolts. The common denominator has been over pressure hand loads. Typically the owners pass it of as the equipment's fault.

[terrywick4]

Broken bolts are a reality for some people who hand load. I think the cartridge unfairly gets the blame. I'm pretty new to this forum but in the short time I've been here I've seen more than one thread about broken bolts. The common denominator has been over pressure hand loads. Typically the owners pass it of as the equipment's fault.

I agree.. some look to push their loads to the extreme and then later in life they are on here wondering why they have a broken bolt.

[rwh]

I broke two bolts on the same day loading 27.2 grains of 8208XBR behind a 123 grain Lapua Scenar with a ​CCI BR4 primer and Lapua brass. After that I pulled the bullets and checked the power weight. That load had been fine for me all summer but spiked badly on a hot afternoon in August. I've seen posts on this forum with hotter loads that that on this site. If you push the pressure in a grendel you are bound to break a bolt eventually.

[LR1955]

I broke two bolts on the same day loading 27.2 grains of 8208XBR behind a 123 grain Lapua Scenar with a ​CCI BR4 primer and Lapua brass. After that I pulled the bullets and checked the power weight. That load had been fine for me all summer but spiked badly on a hot afternoon in August. I've seen posts on this forum with hotter loads that that on this site. If you push the pressure in a grendel you are bound to break a bolt eventually.

rwh;

Personally, I believe it is basically not enough steel on the bolt when using a fat cartridge like a Grendel. Wish it wasn't so but you get to the point where you can't remove any more metal or even the slightest variation in something breaks the part. So guys spend a lot of effort ensuring everything is absolutely perfect when they build a Grendel upper and those uppers work but I dare say that no matter what you do with one, it will not last half as long as a average rack grade 5.56 bolt. I have come to the conclusion that those are the facts and if you want to enjoy a Grendel, have a spare bolt ready to go.

LR55

[sneaky one]

CMMG came up with the larger bolt concept for the Grrr. It's called the Anvil. Re designed upper inside dimensions.

They use a version of the AR 10 bolt. I think DTech uses a version of that bolt in his WSSM calibers also.

Mike Milli, owns Dtech. I'm still looking to go visit him while he makes me a 6.5 WSSM.

He's a 1 man show at his shop in Northern Minnesota.


Gotta find some brass.


For the Grrr, stay just under max loads for bolt longetivity, and accuracy.

[montana]

Colt made a larger variant for the Yemeni military back in 2014 in 7.62X39. The comparison between a standard 5.56 bolt and the larger 7.62X39 bolt starts at the 5.2 minute mark.https://www.youtube.com/watch?v=xovdRJYg_-o

[montana]

Here is a new desighn for the AR bolt:

Young Manufacturing is the licensed manufacture of the HMB bolt.https://youngmanufacturing.net/product/hmb-bolt/ [url]
The HMB Bolt by HM Defense eliminates the pass through cam pin hole and replaces it with a cam pin socket and radiused cam pin design. The new patented design eliminates the natural weak point of Mil-Spec bolts by significantly increasing the amount of metal (and strength) at the cam pin location. The result- NO MORE BROKEN BOLTS!

The HMB Bolt also reduces contact between cam pin and firing pin, enabling smoother operation of firing pin, bolt lugs and aft gas rings. The new cam pin socket also retains lubrication for extended operations.

And not staking the gas key:

https://youngmanufacturing.net/staking-t...6-carrier/

[A5BLASTER]

Here is a new desighn for the AR bolt:

Young Manufacturing is the licensed manufacture of the HMB bolt.https://youngmanufacturing.net/product/hmb-bolt/ [url]
The HMB Bolt by HM Defense eliminates the pass through cam pin hole and replaces it with a cam pin socket and radiused cam pin design. The new patented design eliminates the natural weak point of Mil-Spec bolts by significantly increasing the amount of metal (and strength) at the cam pin location. The result- NO MORE BROKEN BOLTS!

The HMB Bolt also reduces contact between cam pin and firing pin, enabling smoother operation of firing pin, bolt lugs and aft gas rings. The new cam pin socket also retains lubrication for extended operations.

And not staking the gas key:

https://youngmanufacturing.net/staking-t...6-carrier/

That's perrty cool thinking. But how would that make the bolt lugs stronger and less prone to breaking?

I think what they mean is it helps prevent bolt problems at the cam pin hole.