"best" small frame AR 6mm cartridge?

[Winny94]

Best is obviously subjective, but what would be some of the recommendations for a 6mm cartridge that can easily be loaded for a small frame AR? I do reload, but prefer to keep fireforming to a minimum.
Use would be 800 and in steel ringing, small groups at 100 & 200, and maybe the occasional amateur prs type competition (but only a couple a year at most)

Or is the performance gain for those uses negligible enough I should just go w/ a 6.5 grendel.

 

[502Chevelle]

This has been covered here a ton already. Most are going 6 Grendel, 6ART, fat rat, 264lbc etc.

 

[502Chevelle]

Go to page 2 and scroll down about half a page to the thread on 6 Grendel.

 

[mensajd]

Or 243 wssm. See dtechuppers.com. With 95gr Sierra TMK you can shoot accurately out to 1k yds. Higher BC bullets exist but most won’t fit to mag length.

 

[Yondering]

Go to page 2 and scroll down about half a page to the thread on 6 Grendel.

This. Most of the 6mm Grendel variants are basically the 6mm PPC benchrest cartridge with the shoulder blown forward slightly and throated for heavy match bullets. A few take that a step further with shoulders blown out further and require more case forming, but you don't have to choose those if you want to avoid forming.
Mine is the 243 LBC from Black Hole Weaponry. It's super easy to load for (just use Grendel brass, first trip through the sizing die does all the forming you need), and really easy to find good loads for. It's best in long barrels for a flat shooter, and does really well at distance with 95gr-105gr bullets. I'd buy mine again, no regrets.

If I wanted to stick with smaller powder charges and lighter bullets, I'd consider the 6mm/223, just because brass is plentiful, but it's not in the same class as the 6mm Grendel variants for power, versatility with heavy bullets, and ease of finding accurate loads.

 

[sobrbiker883]

Super6 SD. Scott at Specialized Dynamics was necking up 22Noslers to 6mm for a while.
After working w/Nosler, Nosler dropped it on the market in a 24Nosler version. Rebated rim keeps more meat on bolt, like the 22Nosler. Both have theoretical advantages to being able to withstand pressure better in the AR platform than their counterparts (6Grendel and 224Valkyrie).

 

[sobrbiker883]

But the motivation was predator hunting.for the OP’s stated purposes, I choose the 65Grendel. Better wind at 700+ and still drops coyotes in their tracks.

 

[Yondering]

Super6 SD. Scott at Specialized Dynamics was necking down 65Grendels to 6mm for years. It’s now been picked up by Nosler as the 24Nosler.

I see you went back and changed your post from the original statement; that makes more sense. The 24 Nosler has nothing to do with the Grendel case; it's loosely based on the 6.8 SPC case (with some changes of course).

 

[sobrbiker883]

I see you went back and changed your post from the original statement that it was based on a necked down 6.5 Grendel. The 24 Nosler has nothing to do with the Grendel case; it's loosely based on the 6.8 SPC case (with some changes of course).

Yeah, I was having significant brain farting going on and realized I was all jacked as soon as I hit “post”.
Getting old and long days suck.

 

[Yondering]

It happens. A lot of people seem to confuse Grendel and SPC wildcats on a regular basis, no worries.

 

[sobrbiker883]

From his relations w/Nosler he had the 22Nosler in hand for a while pre-release and was playing with necking them up.
Going down with the Grendel’s neck was way before.

 

[sobrbiker883]

Not sure how either of the Noslers (22 or 24) would be considered 6.8SPC Wildcats though, their rebated rim makes the entire base and web of the case completely different than the 6.8 case.
....but I admit I know nothing of the SPC, never did anything for me and seemed to be a bandaid in its original purpose.

(Between tiny keys and spellcheck this phone is gonna drive me nuts!)

 

[Strykervet]

I guess I still like the old 6.5G. My neighbor has a Fat Rat though and says it's a laser beam.

 

[steve123]

Nobody likes forming brass but that gets you about 100 fps extra in the improved versions like the FatRat. Accuracy is still very good when forming, almost as good as formed.

But the 6mmFatRat can be had in a shorter freebore made for repeaters, unlike the long freebore designed for single loading in some of these variants.

I wouldn't get hung up on 6mm specifically since the 224V has come. It's too easy if you go with a good Co like Craddock Precision who has the correct reamer and has his stuff tuned to the cartridge. You get higher BC's for the weight, use less powder, and have less recoil.

 

[Travis224]

Not a speedy cartridge, but a truly fun one is a 6mm Valkyrie. I had the reamer made a week or two BEFORE the 224 Valkyrie was announced as a SAAMI cartridge. Cheap brass, better brass if Lapua makes a batch. Good performance with mod weight bullets.

 

[flyer]

AR15PERFORMANCE makes the TAC6, a 6.8 SPC cat that is necked down and the shoulder bumped back to work with 105 grain bullets (and lighter).

It can beat the ballistics of the .224 Valkyrie in most circumstances with a shorter barrel.

No Grendle bolt issues and works from common 6.8 SPC magazines.

 

[buckshotbarlow]

tac6...run a 22" mower axel from Harrison. I really like the lil cartridge. Running 95gr SMK behind 30.2 ish LVR right at 3k fps. 100% moa at 300yds to the point it gets boring. One thing I found is that brass makes or breaks this cartridge. S&B is the only way to go, fireforming 224valk brass allows for me only about 3 or 4 firings. Federal, Starline and HDY primer pockets are garbage.

 

[LeadZeke]

.243 WSSM cannot be beat from the small frame and Dtech is where to get them. Matches or exceeds .243win.

But if you want double-stack mags then the TAC6 is the way to go probably.

 

[steve123]

Good timing, I was pounding the 1000Y plate this morning with my FatRat, 95smk at 2870 fps. A little windy so had to use 1.8-2 mils of windage. I do like this little cartridge.

 

[buckshotbarlow]

Good timing, I was pounding the 1000Y plate this morning with my FatRat, 95smk at 2870 fps. A little windy so had to use 1.8-2 mils of windage. I do like this little cartridge.

How do u like the the fatrat? i looked really hard it, but i liked the tac6 a little bit more than the fatty. Some of the guys over at barts bullets finally beat some straight ppc's with it...But damn near the same cartridge outside of case capacity.

 

[mkollman74]

FatRat is the route I went. Couldn't be happier. Do yourself a favor and get a brass catcher though. At first it loks wierd, but it sure beats hunting down brass all day. I shot a match with mine with no issues.

 

[bjay]

6mmAR 600 yards 5 shots on rocks
Reference below.

 

[steve123]

How do u like the the fatrat? i looked really hard it, but i liked the tac6 a little bit more than the fatty. Some of the guys over at barts bullets finally beat some straight ppc's with it...But damn near the same cartridge outside of case capacity.

Except for fireforming there isn't anything not to like. Lapua brass and it lasts long if you don't push the case, .059" flashhole, low recoil. My upper has been very reliable.

I try to make first round hits so I use temp insensitive powders, like H4895. Others don't care so much about that and use powders that give more velocity, like AA2520, which can give another 100 fps. I've learned to not try to make a little cartridge any more than it is, been down that road a few times, like when I had 105 Amax going 2915-ish out of a 26" AR-T40 in the mid summer. Put the rifle away and next thing I know it's mid winter before I shot it again. Thought my scope was broke because I was hitting low, mostly under a 10" plate at 600Y, chronoed and had lost 125 fps, lol. Yes I confirmed zero and had accounted for DA.

I tried 243 Win in the AR10 frame, I was surprised at how much more rifle movement there was compared to the 243wssm I had at the time, in spite of it being 2 pounds heavier, that heavy BCG coming back I suppose.

I hated that 243wssm upper because the brass was horrible (worst I've ever seen) as well as it being unreliable and inaccurate, but the upper was a Olympic Arms which isn't known for quality.

The 243 Win was okay but in a 20" barrel I was only getting 2800 fps with 105's, the 243wssm was 150 fps faster in a 24" with the same bullets.

I've had problems with 22 cal Hornady 88's not making it to the target in my 223AI so I'm reluctant to go 22 cal in spite of the higher BC so at this point I'm staying with 6mmFatRat.

 

[sam4886]

I've got a 6mm predator from AR15PERFORMANCE that is pretty damn fun. Same case as the 243 LBC and 6mm grendel. Very simple neck down to form it. 1 run through the die and you're good to go. My newly formed brass shoots just as good as the stuff that is fully formed to my chamber. Shooting 90s at 2830 fps.

 

[hlee]

I've got 2 6.5 grendels, and an upper/lower combination that is a barrel and bolt away from being complete. Is there enough difference between the 6.5 grendel and 6 grendel/predator to warrant going 6mm predator? I'm also considering 224 predator...

 

[sam4886]

Well if you've got 2, you might as well try something else. Hell, I'd probably do 1 of each info were in your shoes.

I'm not brushed up on all the ballistic intricacies right now, but when I was choosing calibers, I'm pretty sure that the 90gr stuff in 6mm was about as good as I could get in terms of drop and drift without going through a ton of fire forming/trimming/sizing.

My 6mm predator load mentioned above shoots a hair flatter than my 143 eldx creedmoor load in my howa if that helps.

 

[buckshotbarlow]

Kewl, might have to get another mower axel from arperformance

 

[bjay]

Kewl, might have to get another mower axel from arperformance

Im selling my 6mmAR turbo 40 °

 

[Constructor]

IMO Norma Grendel brass is the best, it's thicker, will handle more pressure and last longer but it is the most expensive. You have to be careful pushing the pressure on Lapua and even Hornady. The cases will bulge at the bottom flowing into the unsupported area of the chamfer at the breech. Lapua is probably the most consistent/accurate but you have to be sure to use the correct decapping pin or you will destroy it on the very first resize.

I think the 6mm is more versatile 55-105gr bullets. small varmints, yotes, long range target, deer and it will do a better job on hogs than a .223. The 224s may shoot a little flatter and believe it or not it shoots the 80gr ELDs fast enough that the 90s and 95s can't catch it in drift or drop. The 88s may be close but that would need to be tested with the final accurate load at elevation to be sure.

I shoot the TAC 6 out of LWRC SIX8 receivers using Magpul SIX8 mags. Same performance as the 6mmAR with stronger bolts and better feeding...and 30 rnd mags.