Anyone with experience, 6.5 Grendel 20" rifle length upper on Carbine lower

[vaguru]

As stated, purchased a 20" 6.5 Grendel 20" rifle upper for hunting. Planning to use a carbine setup lower with collapsible stock for LOP adjustment.

Haven't been able to try it out due to waiting on optics, mags and ammo. My buddy thinks it may not function due pressure drop with rifle length gas system. Have read some articles that state it should work fine.

Anyone with experience doing this.

Thanks for replies.

 

[TonyTheTiger]

Yes.
Your buddy doesn't know what he's talking about.

 

[longshot2000]

just lighten up the buffers. Start with standard Carbine buffer, add weights if needed.

 

[diggler1833]

I run a XLR TR-2 stock on my 20" Grendel. It utilizes a carbine length buffer, spring and tube (it is not a 6 position tube however). Don't quote me, but IIRC my buffer is an H2. I have a non-adjustable gas block, and ejection is perfect...maybe I just got lucky.

It is the easiest-to-swing pig rifle in my inventory, and runs great. You may need to adjust buffer weights or gas settings, but your proposed combo will certainly serve you well once you get everything dialed in.

 

[LRRPF52]

I have personally tested multiple 20” 6.5 Grendels next to each other after building them for friends.

I had 3x 20” Grendels at the range with the following configurations:

20” Lilja on carbine RET, 2.9oz carbine buffer
20” Satern on carbine RET, ST-T2 buffer
20” Lilja on A5 RET, with an H2 A5 buffer

I’ve also tested several 6.5 Grendels with 20” on rifle RET, rifle buffer, rifle spring. Rifle RET/buffer and A5 RET/buffer felt very similar. H2 in a carbine RET didn’t feel that different really.

All functioned, cycled, ejected, locked back on LRHO.

The carbine buffer felt a little faster in cyclic rate.

These all had correct/ideal gas ports at .094” if I recall correctly.

You can add spring weight with SpringCo Hot White if you go carbine RET with 2.9-3.0oz carbine buffer and it will run well.

Ammunition type is also important. I was shooting 123gr factory ammo.

I wouldn’t have a problem building a 20” gun right now with a carbine RET, H2 or ST-T2, and tune it with SpringCo springs.

Grendel was meant to drop onto existing lowers, and Bill Alexander did extensive testing to make sure complete uppers were an easy swap for the customer base who already have complete lowers. The Mil-Std TDP was used as the reference for this.

 

[vaguru]

Thanks all for replies. Maybe this Friday I'll get to test it out.

 

[vaguru]

LRRPF52,

PM sent. Thanks

 

[BPGuru]

Try it and let us know. Only problem I had was not starting out using a small base die for resizing the brass. Runs perfect now with a standard carbine rear. Good luck with yours.

 

[bobke]

20” rifle gas Grendel on a carbine lower is my preferred setup as well, and you’ve gotten proper advice above, as LRRPF52 has literally written the book/s on 6.5GR. Be certain to lube BCG/bolt and figure 40-60 rounds of ammo to lap in moving parts and break in your barrel. I’ve run a handful of the above spring and buffer combos very successfully, though have settled with JP SCS setups based on personal preference. Grendel can be very accurate, forgiving to load for and quite effective on game. Good luck with project.

 

[hkguns]

I built a 20" Grendel, rifle length gas with an A5 (H2) rear end that works perfectly when I can get it to feed properly. I have no gas related issues at all and the A5 will be harder to cycle than your carbine rear end.

So, as stated above, your buddy is FOS.

 

[vaguru]

For those interested. Able to shoot above stated rifle. Used AA magazines and PPU 120gr factory loads.

Ejection was at 4 o'clock, fed without issue, shows potential for very good accuracy (3/4 MOA) with 9X scope.

Only issue was failure to lock back (about 75%) on an empty mag, bolt caught on follower rather than bolt stop, was only loading 1 round per, sighting in and testing. Tried well used 223 mag, worked roughly 90%+ on bolt stop lock back.
Thinking AA mag followers dragging or possibly inconsistent ammo. Put on full mil spec rifle lower, AA mag same issue so I doubt buffer or spring issue.

Last 10 rounds shot from fully loaded mag, no issues feeding, ejecting or full bolt lock back when empty. All functioned 100%.

Probably just needs more rounds down range.