Anything better for me than a 6.5 Grendel in the AR-15 platform?


Full Member
Mar 16, 2017
Skagit Valley, WA
i think a 6mm grendel would be the way to go. 6mm is a better fit to the grendel brass in my opinion. no fireforming. just neck down the 6.5 grendel brass and go for it.

the 6mm Arc is just another hornady reinvention of the wheel. although they are the only ones smart enough to get their cartridge sammi ed.

The 6mm Grendel variants have always been the way to go. But the difference between them and the ARC is just the shoulder being pushed back .030”. Not enough to matter much, and for someone starting fresh it only makes sense to go with the standardized round.

There is no fireforming required for any of these, to be clear. You can form a 6.5 Grendel case to 6 ARC just as easily as to 6 Grendel; just a single pass through the sizing die, trim, and it’s done for either one.

One more thing (not part of the reply above) - ignore the people claiming to use Pmags or other 5.56 mags for any Grendel/ARC based round. That only works for a few rounds in the mag; more than that and the mag jams up. Don’t believe me, try it yourself, we all have Pmags floating around. You will want to buy Grendel-appropriate mags, but those and the bolt are the only non-standard components needed, other than the barrel.

But - most 6.8 mags do work fine, so there are more options than it appears. For example I’m using some PRI 6.8 waffle mags in my Grendel stash, and they’re one of the best type I have. And with ASC, I have some of each and am hard pressed to tell a difference other than the follower color. FWIW


Full Member
Jul 11, 2010
And, here, is the greatest "issue" with the Grendel cartridges. Mags are a crap shoot. Some people have great success with one brand. Some others have terrible experiences with the same magazines. The only real answer is to try them all and let your gun figure it out.

That, and Elander (and AA branded Elander) 6.5 Grendel mags suck sweaty goat balls. Fuck them...

My findings as well, haha. Tried to get 6 of their 24rd mags working in my suppressed 18" 6.5G and could not get through a mag without multiple failures to feed.

Tried my old 29 or 30rd 7.62x39 ASC mags (pretty sure they're the original/first gen ASC before they got bought and sold/rebranded a few times) and have not had an issue since.

These ASC mags have been used with a suppressed 7" 7.62x39 upper in full auto and are dirty as fuck, but they just keep on chugging along.

If Barret has cracked the code on the Grendel mag for their 6ARC it could certainly give the entire G-based cartridge family a boost.
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Old Man with Gun

Major Hide Member
Full Member
Feb 4, 2019
If target shooting at long distance, yes, 6mm is 10% better than 6.5mm.
If hunting Coyotes the 6mm is 10% better than 6.5mm. (Flatter shooting)
If hunting deer 6.5mm is 10% better than 6mm. (Energy on target)
I would not attempt anything bigger than whitetail with a 6mm.
For factory ammo availability 6.5mm is 90% better than 6mm.
On most things they are very close, but if OP doesn't reload, what matters is can he feed it and at what cost?