CMMG 6.5 Grendel

[Kswhitetails]

For those talking about wall thickness on bolts, consider this:


SCAR-17 on the left, .473" case head diameter, 62000psi max working pressure. Control your metallurgy, and bolt life isn't an issue.

5.56 bolt on the right.

Agreed, LR. However, I'm very interested in a 62K PSI rated Grendel bolt, with large lugs and a deep beefy bolt face and extractor.

I don't believe the Grendel bolt is a problem as is, but wasn't it developed from a bolt designed for another caliber all together(7.69x39), and simply because it was readily available at the time? I am still surprised as much as I have read about the Grendel's development that it's own unique larger-diameter bolt face and barrel extension were never adopted. I realize there is something to be said about parts interchangeability... but in 99% of Grendel set-ups, you're buying barrels chambered in Grendel that already have extensions installed. I don't think adopting and installing a unique extension to match the already different bolt change much in that respect. Admittedly though, I am no firearms engineer, and there are many assumptions that are probably way off on my part. Just throwing out my thoughts as I go along this Grendel journey.

There are reasons the larger cases (in this case Grendel vs 5.56) have additional material in the lugs to support the webbing on the bolt face around the case head. Longevity and reliability being preeminent. I refer to the Anvil's bolt face image above. I can't see how this is anything other than a good idea for the Grendel bolt. Hell, simply adding a few thousandths in the webbings and bases of the lugs would change the strength ratings considerably...

This is America, bigger is better! (with the caveat that we're only speaking about the barrel extension and the bolt face. Leave my lightweight XR15 platform alone...)

[LRRPF52]

Once you use a larger barrel extension, you just killed AR15 parts commonality with one of the most important parts for the AR15 frame.

6.5 Grendel used the .50 Beowulf bolt, which was engineered on the coat tails of the Colt 7.62x39 bolt (something the after-market still has not researched and followed other than Bill A. and Beowulf).

The other issue is pushing pressure from such a small frame, which increases recoil, muzzle blast, sights coming off target, and slower recovery. The thoughts behind it all were, if you push more and make the COL longer, you need a new lower, new upper, new extension, etc. Might as well just go to the larger AR10 frame at that point.

One of the main pivotal pillars of Grendel's success is that you can drop it on an existing lower and go, or build it up on any of the AR15 uppers on the market. That is huge for gaining acceptance from the market.

CMMG has a mid-sized platform meant to handle larger case head dims, starting with 7.62x39, that would also take AK mags on the Mutant lower. They then introduced a .458 SOCOM.

Because the market is so wide, with everyone and their brother competing for shares, I think it made a lot of sense for CMMG to try to expand sales of the Anvil series by going this direction. Some people will be happy with it, while others will want to stick with AR15 compatibility. We'll see how those numbers play out as time goes on.

Either way, one thing is certain, and that is that popularity of 6.5 Grendel is driven by its performance, and a grassroots movement of demand is being fed by response from the ammunition makers.

The Wolf steel case has been a large force in driving this due to the affordability of ammunition.

[Kswhitetails]

Oh, I too am a complete convert to the Grendel. Like you say so pointedly, for no other reason than that of the performance.

My thought is as follows: Why couldn't you ream out the inside diameter of the standard barrel extension a few thousandths to allow for the increased bolt dimensions? .030/.040. As long as the lugs could hold the bolt forward. But with the low working pressure of the Grendel, I would think this to be a lesser issue?

My thought is simply that if you could add some beef to the lugs, walls, and extractor while staying within the 15 platform, you would likely curb the only thing folks complain about the Grendel which is "bolt breakages". I'm with you here, show me the data.

Just a thought.

Not just ammo makers, look at the growth in the Grendel world. If Noveske, CMMG, Larue, see it - then who else is next? People all around the industry are starting to get it. The performance is overcoming the personalities and (supposed) bickering and pride. I have absolutely no doubt that in 30 years, the Grendel will be an extremely common round. It just fits too many pieces together well with too many obvious benefits. Any bets on how long it is till we see 6.5 Grendel MAM/MAUM? >:P

[LRRPF52]

POF actually intruded on the ID of the teeth on the barrel extension for the Revolution, so there is more room for the lugs on the bolt, but that's for a .473" case head (.308 Win.)

It's a good idea to have a balance between bolt lugs and barrel extension teeth, rather than make one smaller than the other.

If you use wider bolt lugs, you are now applying more leverage during bolt thrust against the lug roots of the bolt, unless you increase the OD of the bolt body at the root. For every action, there is some other compromise.

With the CMMG Anvil frame, the hope is to continue the relationship with the customer's trust on buying complete rifles.

With 6.5 Grendel, there is a very strong argument to be made for doing that since the manufacturer can now control everything under one roof and make the gun work from the start.

The LaRue Grendel really made me a believer in that, after decades of not buying factory AR15s, and I do a lot of things during a build now that most builders have never heard of.

[mongoosesnipe]

Oh, I too am a complete convert to the Grendel. Like you say so pointedly, for no other reason than that of the performance.

My thought is as follows: Why couldn't you ream out the inside diameter of the standard barrel extension a few thousandths to allow for the increased bolt dimensions? .030/.040. As long as the lugs could hold the bolt forward. But with the low working pressure of the Grendel, I would think this to be a lesser issue?

My thought is simply that if you could add some beef to the lugs, walls, and extractor while staying within the 15 platform, you would likely curb the only thing folks complain about the Grendel which is "bolt breakages". I'm with you here, show me the data.

Just a thought.

Not just ammo makers, look at the growth in the Grendel world. If Noveske, CMMG, Larue, see it - then who else is next? People all around the industry are starting to get it. The performance is overcoming the personalities and (supposed) bickering and pride. I have absolutely no doubt that in 30 years, the Grendel will be an extremely common round. It just fits too many pieces together well with too many obvious benefits. Any bets on how long it is till we see 6.5 Grendel MAM/MAUM? >:P

from a reliability stand point i actually prefer the bolt to be slightly weaker than the lugs in the extension if you break a bolt lug its potentially a 1 minute fix to swap in a new bolt if you break a lug off an extension there is a lot more to fix and you will need to re headspace the barrel after installing a new extension which is considerably more work than a bolt swap as long as one can accept the grendel for what it is bolt life is 5k+ as long as it was a good part to start with and standard loads will carry to 900m+ before getting trans sonic which is a hell of a thing out of a 6-7 pound gun

as soon as you beef the platform up to start messing with higher pressures to try and make it something its not just go to the thing its not you will be farther

personally i would build a light weight ar10 before i tried beefing up an ar15 im all for innovation and am not afraid of a wild cat cartridge but the grendel is pretty good the way it is

i just got a 6.5 brm barrel for my contender its good for 2500 with 140 class bullets which is plenty during load work up and powder experimentation i accidentally got to 2700 fps there was no harm but the action was stiff to open my goal was 2500 with a powder readily available to be which i found while 2700 seems better there is no such thing as a free lunch and just because something can do something doesn't mean it should

[Kswhitetails]

Agreed here as well. I'm not advocating for reducing the reliability of the system, or interested in the least with increasing chamber pressures. As pointed out already, the G's performance speaks for itself.

[pajasonc]

That has the Anvil receiver set and BCG, with a much larger bolt. Very interesting development.

That's a similar size to the Mutant 7.62x39 rifle they have, but with a lower that takes AR15 mags.

Been saying for years they should take the mutant Upper mod it for normal mags and load it in 6.5 grendel. My original thought was it could be loaded to higher pressures(58k) since thats what the x39 is loaded to. Wonder how much they weight.

[mongoosesnipe]

Been saying for years they should take the mutant Upper mod it for normal mags and load it in 6.5 grendel. My original thought was it could be loaded to higher pressures(58k) since thats what the x39 is loaded to. Wonder how much they weight.

they weigh 8.4 pounds same as a 16 inch ar10

[Kilco]

they weigh 8.4 pounds same as a 16 inch ar10

True, and although I have little interest in the CMMG, I absolutely will take a 8.4lbs 16" Grendel over a 16" 8.4lbs AR10 any day of the week.

I've owned 2 16" AR10s, both DPMS pattern rifles and I despised them. Blast is horrendous, and the ballistics from those cartridges suffer from the 16" tubes. Recoil is also double that of a Grendel.

My only current AR10 is a re-barreled Armalite in 260 Rem with a 24" barrel weighing over 12 lbs scoped.

Although I see your point, no matter how I tried to configure them, an AR10 makes a Clumsy handy carbine. This CMMG Grendel could still be used as such... IMO anyways.

The R-15 in 30 Rem AR I picked up recently has the larger bolt face and barrel extension, and a slightly. Wider upper receiver, yet it still handles and feels like an AR15 even with the 22" barrel. I would take it in the field 10 days out of 10 over a 16" AR10.

[LRRPF52]

Been saying for years they should take the mutant Upper mod it for normal mags and load it in 6.5 grendel. My original thought was it could be loaded to higher pressures(58k) since thats what the x39 is loaded to. Wonder how much they weight.

Are you saying people are hot-rodding 7.62x39 in the Mutant to 58ksi? That bolt and extension plus barrel tennon might take it, depending on how long the lugs and teeth are. Look at the 30 RAR and ask why they were limited to 55ksi SAAMI MAP? Extension lugs aren't as long as an AR10. I suspect the 30 RAR bolt lugs are shorter too. We can ask the forum member with one to caliper his lug lengths.

SAAMI MAP for 7.62x39 is 45ksi. x39 has more thrust at the same pressure because the chamber is so tapered, like a shape charge aimed at the center of your bolt face.

That's the main temptation with the CMMG Anvil though. Those who like to hot-rod will want to push it faster, with higher pressures.

I can think of 2 people off the top who are probably already salivating at the chance to push a 130 or 140 to .260 Rem speeds. The Grendel and 6.8 in the AR15 certainly didn't stop them from doing it already. Maybe they'll get 6.5x284 speeds from this one and rush back to tell us about how safe it is, no pressure signs!

Drag their cases through a bowl of H322, scrape the overflow kernels off, and crunch a bullet down into the case, then head off to the range. Primers will fall out after the first load, but that's a small price to pay in the quest for more speed.

I like CMMG and it's nice to see another complete factory AR chambered in Grendel that has everything controlled under one roof.

[pajasonc]

they weigh 8.4 pounds same as a 16 inch ar10

Yeah thats to heavy for a 16 inch grendel. I wonder how much weight is the extension and bolt. If that had a lighter profile, fluted barrel and lighter handguard it might not be to bad.

[mongoosesnipe]

True, and although I have little interest in the CMMG, I absolutely will take a 8.4lbs 16" Grendel over a 16" 8.4lbs AR10 any day of the week.

I've owned 2 16" AR10s, both DPMS pattern rifles and I despised them. Blast is horrendous, and the ballistics from those cartridges suffer from the 16" tubes. Recoil is also double that of a Grendel.

My only current AR10 is a re-barreled Armalite in 260 Rem with a 24" barrel weighing over 12 lbs scoped.

Although I see your point, no matter how I tried to configure them, an AR10 makes a Clumsy handy carbine. This CMMG Grendel could still be used as such... IMO anyways.

The R-15 in 30 Rem AR I picked up recently has the larger bolt face and barrel extension, and a slightly. Wider upper receiver, yet it still handles and feels like an AR15 even with the 22" barrel. I would take it in the field 10 days out of 10 over a 16" AR10.

im not advocating a 16" 308 or 260 as much as just suggesting you may as well chamber an ar10 for grendel it would be the same weight and allow the bullet to be seated slightly farther out for a modest performance gain if thats what you are looking for that said for $1800 you could use a 20" proof or christensen barrel and come in under 8.4 with a creedmore build

[LRRPF52]

Yeah thats to heavy for a 16 inch grendel. I wonder how much weight is the extension and bolt. If that had a lighter profile, fluted barrel and lighter handguard it might not be to bad.

The 20" DPMS GII is 7.76 lbs. You can get them in 6.5 Creedmoor from a custom shop in Wyoming with an ambi bolt hold/release as well.

A big contributor to weight with the Anvil receiver set is the AR10 diameter BCG, and AR10 diameter barrel shank.

[SHORT-N-SASSY]

Personally, I'm delighted to see another auto-loading option for the can-do 6.5mm Grendel cartridge:

"We shoehorned a bigger cartridge into the gun. . . . Now, impose a Grendel geometry, and you are right at the tipping point." (http://www.65grendel.com/forum/showt...ll=1#post75339)


(https://www.thehighroad.org/index.ph...#post-10298509)



So, what's needed is a little more length in the magazine-magazine well ---


Bottom Line: Let's let experimenters do, what experimenters do!

[Kilco]

Look at the 30 RAR and ask why they were limited to 55ksi SAAMI MAP? Extension lugs aren't as long as an AR10. I suspect the 30 RAR bolt lugs are shorter too. We can ask the forum member with one to caliper his lug lengths.

Did some measuring for you! From top of the lug to bottom it's. 205

Lug width is .176

Comparing it side by side with the Grendel or 5.56 bolts the lug are quite a bit beefier. (Obviously)