School Me On Grendel Barrels

[LRRPF52]

Sir. I have been doing message boards for cars/guns since the 90s. This is probably the most informative, resourceful, comprehensive response I have ever received.Many, many thanks. Much obliged.

I'm thinking, given the data you've expertly disseminated, it's really difficult to not opt for the PF cut Criterion barrel. For my purposes, it'll be as accurate as my needs call for, fluting is an option, and given I won't be on a bench, it'll probably outshoot me.

As no good deed goes unpunished, I have one inquiry lingering. The PF Criterion utilizes an ILGS. While I don't plan on running it suppressed right now or even permanently in the future, it's a possibility I'd like to leave the door open for. It's a little less dwell time than a RLGS. Assuming no adjustable block, is an H2 buffer the proper choice without a suppressor? H1?

You've already been of more assistance than anyone could reasonably expect. I truly appreciate it. Most online forums have devolved into name calling and terrible opinions based on marketing.

Thank you all. Truly. This place is awesome.

That’s why we charge so much for forum membership! :o

If you go with Intermediate Length Gas System on an 18”, it has more ideal plug dwell time compared to MLGS, if shooting 120-130gr projectiles with slower-burning ball powder (common canister powder from manufacturers).

MLGS is great on 14.5” and 16” Grendels, as well as 5.56 NATO.

MLGS 18” is more ideal for 95gr-115gr projectiles with faster powder, though I almost exclusively shoot 120-123gr from my 3x 18” Grendels.

One thing I have seen with hand loads in the 18” MLGS is that if I load with more case fill towards the upper end, the cyclic rate rises into or over the edge of the optimum window of operation.

I actually installed a Bootleg Adjustable Gas carrier into my 17.6” MLGS Grendel for that reason, to choke the gas flow in order to slow down the cyclic rate with one of my CFE223 loads under the 123gr A-MAX.

If I could go back, I would have spec’d out 2 of my 18” Grendels with ILGS or RLGS, and leave one MLGS.

The 95gr Lehigh Controlled Chaos hand loads I have tested behaved exceptionally-well though, with no real felt recoil and a 1.4” 5rd group at 200yds from my lightweight 17.6” Lilja Grendel barrel.

There are detailed discussions on this in the 6.5 Grendel Handbooks we wrote, with diagrams on the different gas system lengths and what type of behavior to expect from each.

Barrel length and velocity
I will also say that I haven’t seen enough of a performance difference to justify 18” over 16” or even 14.5”, but 18” does handle nicely with the right barrel profile.

I have recorded the following average velocities 15ft from the muzzle:

12” Faxon Group Buy Barrels
90gr TNT 2683fps
120gr Federal OTM 2384fps

16” AA barrel
123gr Scenar 2452fps
123gr A-MAX 2439fps
120gr SMK 2470fps

17.6” Lilja Grendel
90gr TNT 2893fps (10 shot sample)
120gr Federal OTM 2484fps (20 shot sample)
120gr Scenar-L 2511fps
123gr SST 2457fps

18” LaRue Stealth Rifle
123gr Hornady American Gunner 2441fps
123gr A-MAX on 31.2gr CFE223 2519fps


Even though I started out shooting a 16” AA and have built many of them, and still have the Lilja 16”, for some reason I shoot the 17.6” Lilja and 18” LaRue more. Could be just down to not having the right optic mounted on the 16” though, because it feels great in the hands with that Wasp profile barrel. There were only a few of the Wasp 16” pipes made for the original Lilja group buy we did here, and I don’t think Lilja ever did them again.

The recoil behavior from the 18” MLGS is manifest in the bolt carrier having more gas flowing into it due to the added plug dwell time, whereas a 16” MLGS behaves nicely, assuming a .076” gas port for each. Neither should have a port larger than .076”.

I have tested 18” MLGS barrels that had .094” gas ports, which really needed adjustable gas turned almost all the way down to choke them, just to get them to function. One such sample I could not get to function in the cold. It either ran with excessive cyclic rate, or short-stroked. I spent more money driving to the range and feeding it than it was worth, which reinforces the recommendations to buy from a reputable barrel maker.

It’s just not worth your time and money to roll the dice or bet on known non-performers.

Never once have I ever said, “Gee, I sure wish I had spent less on this Bartlein, Lilja, Criterion, etc. barrel!”, after experiencing nothing but boring reliability and superb accuracy.

When I used to shoot 2-3x week at a local range for load development or zero confirmation, I typically would bring back targets with tighter groups than almost every bolt gun shooter there. You can tell when you walk down the pit by looking a what everyone’s groups actually are, versus what gets cherry-picked.