Broken 6mmAR Bolt

[LRRPF52]

It's getting to the point that I've been thinking about how I can increase my shoot schedule to purposely try to break bolts just to see where it will happen.

I've lost count of how many different Grendel AR15s I've been shooting over the years now, with everything from RLGS 24", 22", and 20", to 18" MLGS x many, 16" MLGS, and now 12" CLGS suppressed.

12" CLGS suppressed should be the hardest on the bolt since the gas system is so much closer to the chamber, resulting in much higher port pressures.

Maybe drop in the Franklin Armory Binary trigger and stack pallets of Wolf steel case, but for what?

[lazyengineer]

....
Maybe drop in the Franklin Armory Binary trigger and stack pallets of Wolf steel case, but for what?

For the Best TIME EVVAAAHHH!!!

[Kswhitetails]

For the Best TIME EVVAAAHHH!!!

I lol-ed.

[A5BLASTER]

It's getting to the point that I've been thinking about how I can increase my shoot schedule to purpsoely try to break bolts just to see where it will happen.

I've lost count of how many different Grendel AR15s I've been shooting over the years now, with everything from RLGS 24", 22", and 20", to 18" MLGS x many, 16" MLGS, and now 12" CLGS suppressed.

12" CLGS suppressed should be the hardest on the bolt since the gas system is so much closer to the chamber, resulting in much higher port pressures.

Maybe drop in the Franklin Armory Binary trigger and stack pallets of Wolf steel case, but for what?

It would be best if someone other then you did it. Because if you do it, it will just be said that you cooked the results somehow.

[SHORT-N-SASSY]

. . . to purpsoely try to break bolts just to see where it will happen. . . .

Great idea ! But, let's go the route:

"We shoehorned a bigger cartridge into the gun. . . . Now, impose a Grendel geometry, and you are right at the tipping point." --- Bill Alexander < https://www.65grendel.com/forum/show...ll=1#post75339 >


< https://www.65grendel.com/forum/show...ll=1post227010 >




< https://www.tactical-life.com/firear...e-6-5-grendel/ >

Let's challenge both designs:

Using the same barrel length, gas system setup and identical known hot loads, let's test a 6.5mm Grendel-chambered AR-15 against a 6.5mm Grendel-chambered CMMG Anvil: Increase the loads (noting respective velocity increases) with the express purpose of determining the breaking point of the Bolt lugs of the weaker design. Then, continue with the rifle that survived that test, to see how much increased velocity could be obtained. If some 200 fps additional velocity is possible, I think it would be fair to state that we'd opened-up a whole new ball game for an auto-loading 6.5mm Grendel --- the little cartridge that could.

[lazyengineer]

Great idea ! But, let's go the route:

"We shoehorned a bigger cartridge into the gun. . . . Now, impose a Grendel geometry, and you are right at the tipping point." --- Bill Alexander < https://www.65grendel.com/forum/show...ll=1#post75339 >


< https://www.65grendel.com/forum/show...ll=1post227010 >




< https://www.tactical-life.com/firear...e-6-5-grendel/ >

Let's challenge both designs:

Using the same barrel length, gas system setup and identical known hot loads, let's test a 6.5mm Grendel-chambered AR-15 against a 6.5mm Grendel-chambered CMMG Anvil: Increase the loads (noting respective velocity increases) with the express purpose of determining the breaking point of the Bolt lugs of the weaker design. Then, continue with the rifle that survived that test, to see how much increased velocity could be obtained. If some 200 fps additional velocity is possible, I think it would be fair to state that we'd opened-up a whole new ball game for an auto-loading 6.5mm Grendel --- the little cartridge that could.

Interesting. One of the appeals of the Grendel is that it runs on a standard AR; only thing different is BBL, bolt, and magazine (semi-optional on mag even). Changing out upper and lower receivers and BCG, all to satisfy a larger frame system, doesn't have the same curb appeal to me. I have a 6.5 Creedmoor AR10 for when I'm willing to trade convenient weight for power performance. My own Grendel goals are to go as far in the other direction; with as small and light weight and compact a package as mechanically (and legally) possible. So to me, switching up to a "medium frame" specialty receiver set, is not something I'm likely to ever do. Trade off is I can't push the pressures beyond 52k. I would have been more interested if they figured out a way to go half-way in between and still squeeze a slightly bigger diameter beefier bolt into standard BCG and receiver set. Maybe that can't be done, but that would be more interesting to me.

[SHORT-N-SASSY]

< https://forum.snipershide.com/thread.../#post-2376269 >

Hornady.com Ammunition: 6.5 Creedmoor 140-grain BTHP American Gunner, Muzzle Velocity, 24" BBL, 2690 fps

[PrecisionFirearms]

awww heck some guy on barfcom broke a grendel bolt in his 6ar. Running what might be some very hot loads.

So y'all get ready there is probably going to be a 6 months parade of weak bolt post and claims of dangerous chamber's coming around agian.

:d :d :d

[Msalm]

Anyone ever try and build a lightweight AR10 based rifle??? THAT'S the appeal of the Grendel on the AR15 frame... It doesn't do anything for me if you have to add a couple pounds with the ANVIL based rifle....might as well build off the 308 case then.

[A5BLASTER]

Anyone ever try and build a lightweight AR10 based rifle??? THAT'S the appeal of the Grendel on the AR15 frame... It doesn't do anything for me if you have to add a couple pounds with the ANVIL based rifle....might as well build off the 308 case then.

Totally agree the CMMG frames have no appeal to me at all.

Now if someone from this board had a spare ar10 bolt laying around. They can send it to me and I can take some measurements and see if it would be possible to machine it down to fit a standard ar15 bcg.

[centerfire]

Anyone ever try and build a lightweight AR10 based rifle??? THAT'S the appeal of the Grendel on the AR15 frame... It doesn't do anything for me if you have to add a couple pounds with the ANVIL based rifle....might as well build off the 308 case then.

I built a 7lb 16" 308 AR10, it weighs less than my Grendel with a CF barrel. The AR10 shoots amazingly well too. Once you take take the Grendel cartridge out of the AR15 platform it loses most of it's appeal.

[SHORT-N-SASSY]

Under the heading, What our sport shooting world needs is a lightweight 6.5mm Grendel CMMG MkW ANVIL rifle, I today sent the following email to Jeff Overstreet, CMMG Inc. :

[Msalm]

I ‘tried’ with a 338 Federal. Turned the contour down, light stock and forearm, and it was still heavy....and bulky. Not near as nice as a 20” Grendel with carbon fft and ace skeletal stock.

[A5BLASTER]

The only way to get the cmmg grendels to come in at ar15 weight standings is this.

Replace all the internal parts that you can with either titanuim or aluminum parts. Remill the bcg to be really lowmass or have a custom shop build you a aluminum or titanium bcg in a lowmass configuation.

Then take the lower and mill out the side plates of the mag area.

Take the upper and have a custom shop mill in some slots along the length of the upper to drop weight their. Or have a custom shop mill you a lowmass style upper to replace the cmmg one with.

Then loss the buffer and spring it comes with throw in the very best lowmass buffer and spring system made. Slap a adjustable gas block on the barrel after having the barrel re profiled down too .600 and the gas block area re profiled to .625 and then put on a titanuim adjustable gas block and a titanuim flash hider.

Throw on the most stripped down basic stock they make and add a 10 round mag half loaded top it off with a red dot and bam a 7 pound cmmg grendel rifle.

Are you could I don't know safe a bunch of money buy a chronagrah and work up sane loads and never break a bolt.

I have a few irons on the fire right now but I'm gathering materials to do a bolt breakage test.

Handloads will be set at 55k. And we going to see how many rounds it takes to break it.

[SHORT-N-SASSY]

And, the Fims Manufacturing Small Frame AR10 rifle: 7.25 lbs ---



< http://www.gunsholstersandgear.com/shot-show-2019/ >