Caliber choice for my next AR-15 build

EMorr

EMorr

I need a nap
Full Member
Minuteman
Aug 5, 2011
94
160
E. Kalifornia . . . Formerly known as Colorado
#1
I'm a bit undecided at the moment so I thought I would get some opinions on here. Full disclosure I am an AR-15 addict and have several, including 1 stripped lower right now. That lower may very well be my last every AR-15 build, originally I had planned on 50 Beowulf but the more I think about it I'm just not that excited about that caliber any more. So I'm looking for some caliber suggestions for my next build. I already have AR's in 5.56, .300BLK, 7.62X39, 6.8SPC, 10MM Auto and .450BM so those calibers are already off the table. This is a standard AR lower and I don't want to mess with mag adapters so 9mm is also not on the table. Lastly I'm not really concerned about build cost but cost to shoot is a small factor, I don't mind if match bullets are expensive but I'm hoping for a caliber that also has reasonably priced plinking ammo available.

I would very much like to hear what other calibers you guys like in an AR-15 and why.
 
#3
DangerRanger said:
What do you want to do with it?
Click to expand...
Honestly what I do with it will likely be dictated by the caliber I end up picking. A multi role caliber would be ideal, something that can plink (relatively cheaply), can compete (if I get a wild hair) and perhaps take game if completely necessary (larger than varmint would be nice but it's an AR so I'm not taking bear hunting).
 
#7
....a cursory search on ammoseek indicates that imported 6.5G ammo is relatively lower cost, but once you get to the domestic brands, the cost is comparable to 556 & 300BO. If the flow of imports is interrupted, you will be paying domestic costs for off the shelf ammo. You didn't mention having any "longer range" calibers in your current inventory, the new 6ARC would cover that, might consider a complete upper in that caliber and just switch it on/off with one of your existing lowers. The only con of 6ARC is a single producer (at this time) of 6ARC ammo, but if you reload that can be mitigated. For reloading 6ARC, extensive offerings in bullet choices with corresponding costs from low to high, you don't have to stick solely to the heavy stuff (100+ grains) especially for plinking...
 
#8
just did a x39 build and now sourcing ammo. imho, it's the 2nd best caliber option for a AR platform as it's cheap, effective inside 300yd radius, fun to shoot and if you do a sidecharger like I did, makes it that much more fun
cheapest round always
plinking
hunting
etc
 
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#9
I do reload and 6ARC is tempting but the lack of brass and limited factory ammo due to the current shortages make that a tough choice. 6.5 Grendel seems like a really good choice with the steel case ammo.

Does anybody have any experience with 350 Legend? I am also tempted by this caliber and the ability to use 9mm projectiles.
 
#11
EMorr said:
I do reload and 6ARC is tempting but the lack of brass and limited factory ammo due to the current shortages make that a tough choice. 6.5 Grendel seems like a really good choice with the steel case ammo.

Does anybody have any experience with 350 Legend? I am also tempted by this caliber and the ability to use 9mm projectiles.
Click to expand...

....conversion of 6.5 Grendel, x39, 6PPC and 220 Russian has been successfully reported, with the 6.5 Grendel conversion being the most efficient and easiest to accomplish....size, trim, load, shoot ;)
 
#13
50 bmg. Cost per round holding steady last 3 years. It's currently cheaper than 338NM, These are the times we live in. Adapt and overcome.
 
#16
50 beowulf was fun and I wish I never got rid of mine. I have x39 as well and it is fun for blasting, it has a super short barrel so probably not good for any distance. I have a 350 legend in bolt action, but have been tempted to build an ar platform.
 
#19
To be different, 22LR with a folding stock.

Or 9mm with endomags.

For real rifle ammo, the 75gr Federal Valkyrie ammo has been not terribly expensive and shoots .75-1.25 moa out of my guns (.75-1.1 in one and .9-1.25 in the other).
 
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#21
I like my 20 Practical. I have been kind if disappointed with it as a prairie dog exploder though. A 223 with some 55g HPs does better than my 34g Nosler HP at 3900FPS. Maybe the 40s do better, but I bought a ton of the 34g dirt cheap. Practically no recoil on my 18" 20 practical with rifle length gas. Its very easy to watch bullets impact.
 
#22
I've heard the nosler's aren't the greatest. I shoot 39g sierra bk's. I have friends that like the 32's. I shoot a 22" barrel, lots of fun. Honestly though, I still shoot the 17hmr at dogs far more because they are quieter and the impact is much less violent. I shoot to eradicate rather than recreation so I have to focus on not spooking the others. Something about your buddy George's body parts flying through the air after hearing a big POP that sends you running for your burrow.
 
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#23
roostercogburn98 said:
50 beowulf was fun and I wish I never got rid of mine. I have x39 as well and it is fun for blasting, it has a super short barrel so probably not good for any distance. I have a 350 legend in bolt action, but have been tempted to build an ar platform.
Click to expand...
In a SHTF scenario, i think ammo will be one of your most limiting factors as far as firearms are concerned. And .50Beowulf is one of those extremely uncommon rounds.
 
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#26
Jellobin said:
In a SHTF scenario, i think ammo will be one of your most limiting factors as far as firearms are concerned. And .50Beowulf is one of those extremely uncommon rounds.
Click to expand...

...very true. IMHO, if it's a SHTF scenario I think .22LR, 9mm, .223/556 & .308Win/7.62 will be most commonly "scavenged" domestic cartridges and 7.62x39 the non-domestic cartridges.. ;)
 
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#27
They made a turd with the 6 ARC using the Grendel case and mags. Hornady is the dumbest, smart company on the planet.

The reamer makers and Federal ammo fiasco all but killed the 224 Valkyrie which is a kick-ass little catridge. Seems logical Hornady would save face and potentially bale out those burned by the 224 Valkyrie if they would have based the 6mm ARC off the same 6.8 SPC parent case. I mean damn, they already has the tooling/brass for 6.8 and 224.

This is spreadsheet business management at its finest. Something stupid like an excess of 6.5 Grendel brass or tooling may have allowed for additional production of a Grendel based cartridge without impacting the 6.8 based cartridge production. This is only speculation to make my point.

I would have gladly, proud built a Hornady backed 6mm ARC on the 6.8 parent case. No way Im buying a different bolt face, running thinner brass and unreliable feeding mags to shoot the 6mm ARC. Sticking with my 224 Valkyrie AR that I have figured out and my daughters 224 Valkyrie custom bolt gun I built. I built both guns for my kids to shoot long range with low recoil. I survived the 224 disaster with 2 guns that perform well. Only then does a sweet ass 6mm cartridge release in a piece of shit 6.5 parent system. They can keep that shit!

Would be awesome to run a 6mm factory supported ammo in AR and same cartridge in the custom bolt gun….Oh well, some pencil dick at Hornady screwed the pooch on that one for me.

Reminds me of the unicorn 300 PRC which is the longest 30 cal magnum I know of that required special cut CIP length bottom well and CIP magazines to work correctly; oh and this was learned after the fact or at least thats how many people found out.

So short story long……no 6mm ARC recommendation here.
 
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#29
r.tenorio671 said:
....a cursory search on ammoseek indicates that imported 6.5G ammo is relatively lower cost, but once you get to the domestic brands, the cost is comparable to 556 & 300BO. If the flow of imports is interrupted, you will be paying domestic costs for off the shelf ammo. You didn't mention having any "longer range" calibers in your current inventory, the new 6ARC would cover that, might consider a complete upper in that caliber and just switch it on/off with one of your existing lowers. The only con of 6ARC is a single producer (at this time) of 6ARC ammo, but if you reload that can be mitigated. For reloading 6ARC, extensive offerings in bullet choices with corresponding costs from low to high, you don't have to stick solely to the heavy stuff (100+ grains) especially for plinking...
Click to expand...
The 6ARC ammo costs and will continue cost the same as the 6.5 Grendel. It won't be any cheaper to plink with.
 
#31
Of the calibers you dont own, I would think 6.5 Grendel is the obvious choice. Especially if you reload. I wanted to do my recently completed build in 6.5 Grendel, but the reports of feeding/reliability issues turned me off. I chose instead to do a "dream build" in 556 with a 14.5" barrel and it was a great decision. I went with my approximation of the best parts available with very little budget constraint. I plan on developing a load for this gun specifically with 69 or 77 grain SMK or perhaps one of the heavier Barnes TSX bullets.
This convinced me that there is more to a build than caliber choice.
 
#32
If you don’t have a precision 5.56 gun with a medium/heavy profile Bartlein, Krieger, Rock Creek, Proof, etc barrel, you should.

If you have everything covered, spend the money on spare parts to keep the guns running long term.

If your optics are shit, use the money on a good optic.

You can never have enough ammo.

If you still just want a new round, 6.5Grendel.
 
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#34
I personally would look at the 6.5 Grendel, there are more affordable ammo options for it from several sources.

I do like the ARC, but I have so much reloading supplies for the Grendel I would take a big loss selling it to get into a 6 ARC. The Grendel has been my favorite little round to shoot
 
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#35
waveslayer said:
I personally would look at the 6.5 Grendel, there are more affordable ammo options for it from several sources.

I do like the ARC, but I have so much reloading supplies for the Grendel I would take a big loss selling it to get into a 6 ARC. The Grendel has been my favorite little round to shoot
Click to expand...

...FWIW, the Hodgdon Load Center lists multiple common powders that are compatible with both 6ARC & 6.5 Grendel in bullet weights 85-107 grain with similar if not same FPS achieved. It's only above the 107 grain projectiles that the 6.5G differs.
 
#36
r.tenorio671 said:
...FWIW, the Hodgdon Load Center lists multiple common powders that are compatible with both 6ARC & 6.5 Grendel in bullet weights 85-107 grain with similar if not same FPS achieved. It's only above the 107 grain projectiles that the 6.5G differs.
Click to expand...
Yep very well of that. What I stated was there were affordable options like Wolf ammo etc for the Grendel. That's all👊🏻
 
#38
Jsp556 said:
If you don’t have a precision 5.56 gun with a medium/heavy profile Bartlein, Krieger, Rock Creek, Proof, etc barrel, you should.

If you have everything covered, spend the money on spare parts to keep the guns running long term.

If your optics are shit, use the money on a good optic.

You can never have enough ammo.
Click to expand...
All of our enemy that have been killed with the 5.56 are still dead.

There is a tremendous variety of ammo available in 5.56, Everything from bulk 55 grain to precision 77 grain hand loads.

My Noveske N4 Switch Block topped with a Leupold MK-8. It is a half inch shooter with the good stuff.

IMG_1257.JPG


IMG_1315.JPG

IMG_1314.JPG
 
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