6.5 Grendel Forum
Bolt Breakage Risk? - Printable Version

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Bolt Breakage Risk? - NightStalker - 07-04-2020

Has anyone had an issue with type 2 bolt breaking?

I was emailing back and forth with a SF soldier i know who is of the opinion that the 6.5 Grendel is not a combat round because of weak bolts. I thought this issue was fixed?

Bolt Breakage Risk? - VASCAR2 - 07-04-2020

First recipe for a broken 6.5 Grendel bolt is running ammo that is over 52,000 psi. Short chambers or jamming bullet into lands can contribute to premature bolt wear. Poor QC or heat treat for 6.5 Grendel bolts can be an issue but most recently there haven’t been many reports. Usually a poor quality bolt will fail pretty quick.


The AA, Maxim, Toolcraft and Millennium Monster bolts have very good track record. Run a search of this forum and see how many hits you get. One forum member broke a couple bolts using IMR8208XBR and 107 SMK. Make sure your receiver face is square and watch your reloads and I doubt you’ll have broken bolts.

Honestly bolts and extractors are consumables like brakes on a car. Bolts won’t last forever but I never personally been around anyone who broke a 6.5 Grendel bolt. I had to replace an extractor on an over gassed 16” carbine gas 6.5 Grendel. A Friend had to replace a extractor on way over gas 18” Satern/Liberty MLG barrel. An adjustable gas system has prevented any other problems.

It is not a good idea to run a 6.5 Grendel over gassed, especially mid length gas 18” barrels with suppressors. If running a suppressor it is wise to use an adjustable gas block, adjustable gas key or adjustable gas carrier.

Here is a link to the google custom search feature for this forum.

https://cse.google.com/cse?cx=016368947416500061353:paqd_0xcu1o&hl=en

Bolt Breakage Risk? - A5BLASTER - 07-04-2020

Haven't broke one yet and don't know anyone who has.

Seen some on the grendel Facebook page and 99% percent of the time it was either handloads way over pressure, a highly overgassed rifle that was the cause of the issue.

Lapp the upper and keep the rifle properly gassed for a 3 to 3:30 ejection pattern don't try to turn your grendel into a creedmoor with 60k handloads, buy a known high quality bolt and bolt breakage won't be a problem.

All bolts will break no matter what caliber the bullet in the end of the case.

Bolt Breakage Risk? - NightStalker - 07-04-2020

Its a lapped Aero upper, Ballistics Advantage SS barrel, a tool craft type II BCG and the gas block is adjustable just don’t remember the maker. Been rounding up ammo and mags so haven’t even got to shoot it yet.
I did a search before posting not many hits, just thought id ask.

Id post a pic but it keeps saying file to large no matter how much I shrink it

Bolt Breakage Risk? - VASCAR2 - 07-04-2020

The file size has to be almost thumb nail size to upload directly from your device. I use a free web hosting site Flickr to post pictures. There are several other free web hosting sights like imgur, postit which are also popular.

Bolt Breakage Risk? - NightStalker - 07-04-2020

VASCAR2 Wrote:The file size has to be almost thumb nail size to upload directly from your device. I use a free web hosting site Flickr to post pictures. There are several other free web hosting sights like imgur, postit which are also popular.

Is this an app to be downloaded

Bolt Breakage Risk? - VASCAR2 - 07-04-2020

You can sign up for a Flickr app or upload individual pictures to your account from your device. I have the app and it wants to upload all my photos. I don’t want all my photos on the Flickr site so I use the website to upload a few pictures I want to upload for posting on forums. I previously used photobucket till they started charging a monthly fee.

Here is a link if you want to set up an account on the web site or you can download the app from the app store.

https://www.flickr.com/

Bolt Breakage Risk? - danm - 07-05-2020

Well considering that 6ARC uses Grendel bolts and has been allegedly adopted by SF... Sounds GTG to me Smile

Bolt Breakage Risk? - FLshooter - 07-05-2020

I have never broke a bolt in an AR 15. And I don’t know anyone who has. I have heard of this happening. But it had to be due to high pressure ammo.Stay within specs with your hand loads and you should be fine.

Bolt Breakage Risk? - Klem - 07-05-2020

Agree with the guys...I haven't broken a bolt and don't know anyone who has. Only heard it on this site.

Bolt Breakage Risk? - danm - 07-06-2020

Klem Wrote:Agree with the guys...I haven't broken a bolt and don't know anyone who has. Only heard it on this site.
Broken extractor... YES, recalled PPU... Yes. Zero busted bolts so far Smile

Bolt Breakage Risk? - LR1955 - 07-06-2020

FLshooter Wrote:I have never broke a bolt in an AR 15. And I don’t know anyone who has. I have heard of this happening. But it had to be due to high pressure ammo.Stay within specs with your hand loads and you should be fine.

Well, I have sheared lugs on three Colt 7.62 X 39 bolts in a Grendel, one AA Grendel bolt, and a machined out 5.56 bolt. I have also sheared a lug on a Grendel bolt in a 6 AR.

However -- these bolts were before the enhanced bolts that seem to be holding up well today. Before these enhanced bolts, there were periodic reports on the forum of guys shearing lugs. It was not uncommon and seemed to plague the Grendel until adjustable gas blocks and the enhanced bolts.

LR55

Bolt Breakage Risk? - biodsl - 07-06-2020

NightStalker Wrote:I was emailing back and forth with a SF soldier i know who is of the opinion that the 6.5 Grendel is not a combat round because of weak bolts.

Someone had better call Hornady and the DoD unit that have been fielding the 6mmARC!

Bolt Breakage Risk? - NightStalker - 07-06-2020

biodsl Wrote:Someone had better call Hornady and the DoD unit that have been fielding the 6mmARC!

Im still really new to the Grendel but trying to learn, with that said whats the 6mm ARC and we have units fielding it?

Bolt Breakage Risk? - VASCAR2 - 07-06-2020

NightStalker Wrote:Im still really new to the Grendel but trying to learn, with that said whats the 6mm ARC and we have units fielding it?


For several years shooters have used the 6.5 Grendel case for several Wildcat cartridges. The more common in .243/6 MM are the 6 MM AR, 6 MM Turbo 40. Hornady developed a new Cartridge 6 MM ARC (Advanced Rifle Cartridge) and had a press release a couple months ago. There is a long thread in the new products section on this forum, linked below. Hornady basically used the 6.5 Grendel case, necked it down to 6 mm and pushed the 30 degree shoulder back .03”. Hornady along with several manufacturers have been working with certain military units for a couple years. Hornady submitted the 6 MM ARC and got the cartridge SAAMI accepted. The 6 ARC is still limited to 52000 PSI just like the 6.5 Grendel but has more velocity with higher BC bullets.

Hornady was supposedly trying to meet a design request to meet a military proposal for an intermediate cartridge. Hornady says the military has tested and used the 6 ARC. Hornady and their partners are releasing the 6 ARC and other products to the civilian market.


http://www.65grendel.com/forum/showthread.php?21694-6mm-ARC

Bolt Breakage Risk? - LR1955 - 07-06-2020

biodsl Wrote:Someone had better call Hornady and the DoD unit that have been fielding the 6mmARC!

BD:

The shearing of bolt lugs is nothing new. Before the enhanced bolts it was not uncommon for someone to post about a bolt shearing one or more lugs. Post enhanced bolt and the number of guys posting that they sheared lugs dropped significantly.

I think some of it was due to factory Grendels being grossly overgassed and some due to the bolt design and metallurgy at the time.

The 6 ARC in the military is probably for specialized units and if their armorers are told to change out the bolt on a schedule or based on use then they change out the bolt. The thing is that if they shear lugs, no one here will find out except for rumors. And if the bolt is a weakness then I imagine someone will re-design it so it is no longer a weakness.

A problem guys will find with the various 6mm versions of the Grendel will be barrel wear. It is scary how fast the various 6mm cartridges will erode the throat in a barrell. The 6 AR and 6 ARC will last longer than a 6 X 47 but a regular old 6.5 Grendel will go four or five times longer than a 6 AR or 6 ARC.

LR55

Bolt Breakage Risk? - BluntForceTrauma - 07-07-2020

I've screen-grabbed and attached some thoughts on the Grendel bolt by Bill Alexander, it's creator.

Bolt Breakage Risk? - biodsl - 07-07-2020

LR1955 Wrote:BD:

The shearing of bolt lugs is nothing new. Before the enhanced bolts it was not uncommon for someone to post about a bolt shearing one or more lugs. Post enhanced bolt and the number of guys posting that they sheared lugs dropped significantly.

LR55

I was joking around. I've fired around 5,000 rounds on a couple of Grendel bolts and haven't had a failure. I'd suggest shearing bolts is a historical problem.

Bolt Breakage Risk? - Fess - 07-07-2020

It appears that bolt quality has improved over the years, but I think that another part of the problem early in the Grendel's life was that handloaders routinely were loading to too high a pressure. It seemed to take a while for some to realize that the pressure spec of the Grendel was limited to 52K psi to assure good bolt life in an AR15-based platform. The case, on the other hand, could tolerate higher pressures, so loading until typical "pressure signs" were clearly visible meant that the bolt was overloaded. There is now quite a lot of good reloading information available for the cartridge and the experienced people on this site let newcomers know to stick to tested loads.
When the Grendel was new cartridge, I remember a discussions of WHICH overpressure signs to use. Bill Alexander quickly stressed that ANY overpressure signs indicated well over 52Kpsi.

Bolt Breakage Risk? - Kswhitetails - 07-16-2020

I think the early problems stemmed more from the manufacturers cutting corners with material, heat treat, or using cheap X39 bolts. The Grendel bolt still isn't perfect, they seem to come mostly with sharp edges, extractor corners, ejector holes, and machining marks that other bolts (5.56) don't. But the materials, heat treatment, and machining issues that led to brittle lugs early in the game seem to have been all but eliminated. I found it funny that back when a lot of the complaints of this were common, guys had used the cheapest bolts (to be fair, there was also a rather significant wait time for many of the good bolts at the time) in their builds, ran hotter loads than they probably should have, and immediately assumed it was the Grendel's problem. It wasn't. Funny how JP was able to build a bolt that worked, and didn't seem to fail, regardless of how hard some early testers pushed their builds...

It was the common issues that come with development; and some market T&E that every cartridge that pushes the limits of it's platform like Grendel does in the AR will have. Manufacturers had to figure a lot of this out, and early on it was more challenging making Grendel bolts than running a batch of 5.56 bolts which was so well understood by then that it's production processes were on cruise control... Growing pains so to speak. In most everything I've read, the only guys that had issues getting replacements or service were the type of assholes that I wouldn't want to deal with either...