Grendel AR pistol

[Huntchic]

Thinking of building an AR Pistol in 6.5 Grendel. Have a 18” Grendel now. I’ve got all the parts except the barrels in my spare parts. I’ve also got a 300 blackout pistol I could convert as well. My question is basically about building a 6.5 vs 5.56 or 300 blk.
is there anything “different” about building a 6.5 Grendel or its parts than other calibers I should look out for or do differently?

[LRRPF52]

My 12” Grendel suppressed is my favorite length so far of them all, and I have 22”, 2x 18”, 17.6”, 16”, 14.5”, 12”, 10.5”, and 8.5”. Still working on the 10.5” and 8.5” looking for glass mainly and some other things.

I’ve been shooting the 12” regularly since 2017 now, after several years of mainly leaning on the 17.6” Lilja Grendel. Ballistics are negligible between the two. I shoot the 12” mainly from 300-900yds on UKD 12-18” steel plates every month.

Biggest thing is managing the gas system and action spring, but the port diameters for Grendel match up with 5.56 barrel/gas system length so it isn’t a big deal.

I built 2x 12” Grendels with the same core parts, but different receivers. I used Bootleg adjustable gas carriers since we were both running suppressed, and I used extra power action springs with normal 2.9oz carbine buffers.

I prefer the Rexus Grendel bolts, which are probably the strongest on the market right now. I used the predecessor models from SixFive Outfitters with the Monster logo, and they both are trucking along through thousands of rounds so far. That includes a lot of 2-day DM courses shooting all-day.

I de-edge, blend, and polish all my Grendel barrel extensions for smooth feeding and babying of brass.

I also chamfer my ejectors so that there’s no way for the case rim from right side mag presentation to hang-up on the side of the ejector.

I ensure the receiver faces are square with a lapping tool, and bed or press-fit the barrels into the upper with an extremely tight fit based on parts-selection with the upper and barrel extension diameters, along with Cerakoting the extension tunnel inside the upper. I make sure no Cerakote is applied to the carrier raceway because I don’t want to mess with raceway ID and sluggish carrier momentum.

I bed the gas blocks and won’t use a slip-fit gas block if I can help it. I also ensure the gas tube is aligned with the carrier key without clipping.

Muzzle device gets minimal torque and Rocksett, especially for suppressor brake-attach.

Drop in a quality trigger from LaRue, Geissele, or Trigger Tech, top with quality glass and off to the races.

The main advantage you’ll have with a little Grendel is ease of carry in the woods for hunting and a nice, manageable blaster that has very minimal recoil where you can spot your own hit on the hide and not doubt where your shot went.

[Huntchic]

Thank you for your replying back. So in a nutshell there isn't really anything out of the ordinary between building say a 5.56, 300 Blk or the 6.5 Grendel in a pistol. I have no intention of putting a Can on it but who knows maybe someday ill change my mind. Just for myself i pretty much always go with an non adjustable gas block for its simplicity. I use different springs or buffers to get the desired effect im looking for. Im kinda one who likes less complicated and less things to go wrong. If i was using a Can at times i can see where a adjustable might be nice idea.

[VASCAR2]

My vote is for a 12” 6.5 Grendel. To me the 12” 6.5 Grendel is very pleasant to shoot using an A-2 flash hider. Short 5.56/223 AR-15’s seem to have more blast than my 12” 6.5 Grendel. Suppressors are unlawful where I live but the only advantage I see with the 300 Blackout is if you shooting subsonic suppressed. Ballistics from any barrel length favors the 6.5 Grendel super sonic ammo over the 300 BO super sonic ammo.

I have a 12” 6.5 Grendel from 6.5 Outfitters “Rexus” monster logo barrel which I really like.



12” 6.5 Grendel AR-15 pistol next to 16” Tavor 5.56 bullpup.

https://rexusoutfitters.com/ar15-barrels/

[Huntchic]

I agree. 300 was bit better up closel than 5.56. I agree 300 is great suppressed indoors especially. Since I started learning about 6.5 Grendel I don’t really see a reason to not convert my 300 blk over to 6.5. I’ll just have to have a big range day and shoot up a bunch of 300 ammo. I’ve got a brother who’s a big 300 blk shooter so I’ll have to give him some ammo n brass. I plan right now to get a barrel n bolt next week or 2 then switch it over to Grendel.

[lazyengineer]

The 12" Grendel is the most optimized firearm configuration you can get. Incredibly small and handy, and just look at this







1000 ft-lb impact energy out to 150+ yards. Supersonic flight out to >750 yards. 28 round action shooting magazine capable with mild recoil. In a tiny TINY gun. When you could get Wolf Steel for 25 cents a shot, for plinking, it truly was the One Gun For All Things ULTIMATE - gun.

The only gun I want more, is the same thing in an RDB, for the 17" BBL and still smaller. But for now, this gun, is one hell of a gun. And they can shoot too. FUN little gun. And yes, if you like a suppressor, it's a tidy host for one. But no, you don't have to run a suppressor, it's fine; see how mild the recoil still is, and nobody fell down clutching their ears. Here, here's a clip of a soccer mom at an Eclipse viewing party trying one while we were waiting for the sun to go out.

https://rumble.com/v4ovgth-a-mom-shooting-6.5-grendel-12-at-200-yards.html

For now, you can get it with an ArmBrace again - and likely indefinitely. Do that! Easy! I SBR'd mine, and if I cross state lines I'll toss the armbrace back on (it literally gets redefined as a pistol the moment you do that - no paperwork). Though if you do go armbrace, I don't really advise taking any photos or video of you shouldering it. The case that came out this week was a nice win, but it was a win that armbraces are legal and legal to be used as armbraces. It didn't actually repeal SBR NFA, and it's not in your best interest to leave a trail showing you are using and intended to use it as a shoulder fired gun via armbrace. JMHO.

[Huntchic]

Thanks for that information LazyEngineer. I agree on pictures n videos. I’m curious as to what velocity I’ll get with the 90 gr TNT or a 120 -125 bullet from my build. I figured a 90 gr to 125 be about right for it.

[Huntchic]

What muzzle device do y’all run on a 12” Grendel? I don’t use one on my 18” rifle, just a thread protector. I was thinking of running a flash can. Thinking of using a 13” handgaurd like a Faxon carbon with 12” barrel and a 2”-3” flash can. Would basically end up 14-15” so might defeat purpose of being short and be better to do 16” with thread protector be only 1” longer. I’ve got a bunch of different length handgaurds in parts so might be better off running a 10.5” rail and A2. Any suggestions on a muzzle device?

[LRRPF52]

My 12” spits the 90gr TNT at 2700fps suppressed. 120gr Federal OTM is ~2400fps. What more to ask for?

I like it with the TBAC Ultra 5, but I would probably get a TBAC Magnus-K now, which didn’t exist at the time.

Ultra 5 doesn’t even feel like there’s a muzzle device on it, since it weighs 5.4oz. 100% Titanium

Ultra 5 Gen 2 weighs 6oz.

I’m working on some projectile development right now that will do 3370fps from the 12” Grendel, 3500fps from 14.5”, 3560fps from 16”, 3640fps from 18”, and 3700fps from a 20”.

Basically turns Grendel into a .22-250 with better wounding mechanism due to projectile diameter/construction. Should zap deer and hogs like lightning.

[Huntchic]

That sounds interesting. Keep us posted on how it goes.
I’ve taken a few deer and truck loads of groundhog with the 22-250. Great rifle.

[Huntchic]

That sounds interesting. Keep us posted on how it goes.
I’ve taken a few deer and truck loads of groundhog with the 22-250. Great rifle.

[PharmerJon]

I’m working on some projectile development right now that will do 3370fps from the 12” Grendel, 3500fps from 14.5”, 3560fps from 16”, 3640fps from 18”, and 3700fps from a 20”.

Basically turns Grendel into a .22-250 with better wounding mechanism due to projectile diameter/construction. Should zap deer and hogs like lightning.

Oh my! I’ll be waiting anxiously for this round to be revealed!
-Jon

[LRRPF52]

6.5 Grendel will deliver what the Small Caliber High Velocity Rifle concept never could with the .222 Remington Special (5.56x45), and will do it from much shorter barrels.

The very first prototype AR-15 had a 22” barrel, because SCHV called for really high velocities in order to perforate the M1 steel helmet and a 0.135” steel plate at 500yds. This required a 55gr at 3300fps, but trade-offs were made along the way to reduce chamber pressure and specify a cartridge that could be mass-produced with steady supply of consistent propellant. In production of the M193, we typically have seen 3150-3250fps muzzle velocities.

There was earlier work in the 1940s and early 1950s necking down all sorts of cartridges to .224”, chasing really high velocities, but the cases were not efficient for the application and there was a lot of over-bore, besides those based on the .30 Carbine. The .224/.30 Carbine wildcats were nice, but limited in projectile weight and velocity, while spiking chamber pressures beyond what was acceptable/practical.

Because 6.5 Grendel has more case capacity than 5.56, and a more efficient case design, it does a lot of work even with less chamber pressure. We have just been fixated mainly on 100-130gr bullet weights, with 123gr being the most common. Once you explore it in some of the other weights, it really surprises you.

[Huntchic]

There is always a better mouse trap to be built.
I've been thinking on what bullet would be best in the new Grendel build. seems like the 129gr. ABLR would be an excellent choice to me for its lower velocity expansion.

[Huntchic]

So I’m getting ready to order barrel n bolt but having second thoughts on barrel length. My original plan was to convert 300 blk pistol to Grendel pistol with 12” barrel. I’m now thinking that I might be better off doing a 16” barrel. It’s only 4” more length and very minimal weight difference but better ballistics. I’ve already got a 18” Grendel so 16” is not really much different. Kinda torn now between building a 12” pistol or 16” “rifle. Either way I’m going to do a LPVO on it. The idea is a truck gun that is also for an also for hiking/ hunting gun. I’m about 60% pistol and 40% rifle right now. I know the 12” is basically a 200 yd or less gun and 16” about 300 yards. I’m not so much about the distance but more about energy on target for a med size critter out to 150 yards. Going to try to decide by next day or 2.