Ar15 6mm arc upper

I recently took the plunge. Couldn't find an upper I liked, so bought an 18-inch PSA in 6.5 Grendel (same bolt) and replaced the barrel with a 24-inch from EABCO. Sold the Grendel barrel to offset some of the cost. Upper has functioned flawlessly thus far and happily sub MOA with Hornady factory loads.

Ok, stuff about the 6mm GRENDEL.. Hmmm. It’s expensive. Carries fewer rounds in a magazine. Won’t see the accuracy a Bolt Gun can deliver with the same cartridge. Not as good as many other 6mm cartridges. Yet another of the long list of “fan boy” choices for the AR. Doesn’t have near the reloading range of 223 in bullet/powder selection.

It’s nothing but a new name & 6mm loading for the sucky 6.5 Grendel. Oh wait… pros…. Uhhh, it’s an AR. That’s a pro.

Seriously, if you like it go for it. I was never a fan of the Grendel, and this is the same thing but in 6mm. Honestly, I would do this over the 6.5 Grendel, but for me, 223 is the only thing in my ARs. Been building & running them since 2005, and 223 is always my choice. I believe anything else belongs in an AR10 or better yet, a Bolt Gun. To each their own though.

David Hoback said:

Ok, stuff about the 6mm GRENDEL.. Hmmm. It’s expensive. Carries fewer rounds in a magazine. Won’t see the accuracy a Bolt Gun can deliver with the same cartridge. Not as good as many other 6mm cartridges. Yet another of the long list of “fan boy” choices for the AR. Doesn’t have near the reloading range of 223 in bullet/powder selection.

It’s nothing but a new name & 6mm loading for the sucky 6.5 Grendel. Oh wait… pros…. Uhhh, it’s an AR. That’s a pro.

Seriously, if you like it go for it. I was never a fan of the Grendel, and this is the same thing but in 6mm. Honestly, I would do this over the 6.5 Grendel, but for me, 223 is the only thing in my ARs. Been building & running them since 2005, and 223 is always my choice. I believe anything else belongs in an AR10 or better yet, a Bolt Gun. To each their own though.

Click to expand...

An AR15 built right can produce sub half minute accuracy pretty regularly and many more do today than they did 10-20 years ago. Things have changed.

Your forgot 6mm doesn’t burn a barrel out as fast! Thats a plus.

And a 223 is not more accurate than a 6mm ARC so what is the point of saying that it wont see the accuracy of a bolt gun? By that reckoning a 223 wont see the accuracy in an Ar15 than that of a bolt gun which makes your point moot!

The most important thing i find wrong with your post is that your a fan of 223 but your calling someone else a “fanboy”. Kind of hypocritical don't you think?

Also why is capacity important to everyone? Or did you mean just to you?

If the Ar15 was only in 223 then it would detract heavily from its value as as a Versatile platform would it not? For that matter the 224 Valkyrie outperforms the 223 in distance and energy plus has the same capacity so why is it not better?

Misplacedtexan said:

Looking to buy a 6mm arc upper, pros and cons.
What's y'all's opinion?

Click to expand...

If your looking to build a precision Ar15 its a great time to do so if you have the money.

If your looking to shoot precision and not burn barrels as fast as some calibers the ARC is a good choice for a Reloader. I cant say factory ammo will give you what your hoping for though.

A negative is components being in short supply for a reloader. Especially in primers and certain brass.

I cant say for sure about reloading dies supply in 6 ARC but your going to want good dies for precision reloading. Redding makes some good dies and so does Forster ( my preference ) but they have had supply shortages so another thing to check out and consider.

It might be a little harder to find a precision built upper in 6mm ARC too. 6mm ARC is popular but not sure its as available in an upper so I would make sure there are some options out there before you go all in.

Many people opt for putting their own barrel on an upper (as has already been mentioned) over buying complete because there are a lot more options for barrel brand, sizes, and types. My choice as well. YMMV.

Misplacedtexan said:

Looking to buy a 6mm arc upper, pros and cons.

Click to expand...

6arc has a lot to recommend it. In very round numbers, it's a .243 that fits in an AR15 mag well.
My number one beef with 6arc is that it's so popular , no one seems to be able to stock barrels, let alone uppers in it.
In my perfect world, I'd probably have a 16" Carbine barrel and a 20" rifle barrel upper.

I recently purchased a 6mm ARC chambered CMMG Endeavor. That gives me ARs chambered in 5.56, 6mm ARC, 6.5 Grendel, 6.8 SPC, 300 BLK and 458 SOCOM at this point. All of them are reliable, though the 458 took a little bit of tweaking. Apparently there’s only one guy on the internet who can’t figure out how to make cartridges other than 5.56 run reliably in an AR and unfortunately, he resides here at THR and feels the need to assail us with his truth nuggets every time an AR is mentioned in a chambering other than 5.56.

Moving on, the 6mm ARC is a fun cartridge. I’ve taken mine out to 800 yards a couple times and I’ve been pleasantly surprised at how it holds up at that range. Mine is not the most accurate rifle I own, or at least I don’t think it is. I haven’t really gotten behind it and tried to shoot tiny groups with it. I got it zeroed and started shooting it at longer distances. I do intend to spend some time with it Wednesday and if things go well, I’ll get to test it on some meat Wednesday night. I’ve been impressed with 6.5 Grendel and 6.8 SPC on pig hunts. I don’t see why the 6 ARC would be any different.

It’s a buyer’s market right now. Buy an upper. The pros are low recoil, high BC bullets, compatibility with most 6.5 Grendel components and it puts some more variety in your tool box. The only con I can see is the expense of buying ammo.

My biggest problem with the 6mm ARC is that it came out after the Valkyrie.
I think the 6mm ARC is the best balanced long range AR15 cartridge to shoot mag length with a 20" or shorter barrel.

My buddy build a 6 ARC and it's a hammer. Three hits on 800 yards fired in as many seconds. It's an interesting cartridge.

A friend built one, he converted a 18"Grendel upper he had installing a Faxon barrel. I don't see many complete uppers offered but they are easy to build and when I buy one I remove the barrel and lap the upper and check everything so basically I'm building it anyway. As said earlier it uses Grendel BCG, mags and you can convert 6.5 Grendel brass to 6 ARC

Unless you are set up with reloading equipment and components, I think it is a bad time logistically speaking to introduce a new caliber like that into an inventory that isn't truly mainstream.

FL-NC said:

Unless you are set up with reloading equipment and components, I think it is a bad time logistically speaking to introduce a new caliber like that into an inventory that isn't truly mainstream.

Click to expand...

I reload. When I buy/build something that's unusual, and plan on shooting it regularly, I always buy enough brass to toast the barrel. That's what I did with my 6.5 Remington Magnum and my .300 H&H Magnum. I would not build something without a stockpile of brass.

Good Luck

I was shooting 243LBC for a few years before the ARC dropped - a straight 6 Grendel, fitting about a grain and a half more powder in the case and outrunning the ARC by about 100fps, but for all intents, it’s an ARC… once the ARC dropped, I was glad for a factory option with broad market support. I shot Grendel (and every other damned thing available or even remotely possible in the AR) for the ~15yrs before that, including some of the original group buys from Wild Bill himself…

At ~500fps slower, the ARC isn’t “a 243 [win] which fits into an AR.” It’s only 2/3 the case capacity at only 85% the pressure… it ain’t a 243win…

There’s nothing difficult to source about 6 ARC compared to any other cartridge in the market right now - brass and ammo have been incredibly well supplied relative to the current market - reminding here, this cartridge was introduced during the greatest drought of ammo and components since WWII.

Folks like whining online these days, but reality is far less sensational. The ARC is a very high BC bullet at moderate speeds, low recoil, low cost, long barrel life, its performance aligns with small game through deer hunting demands perfectly, and it fits into America’s favorite rifle…

I would love to try out the 6mm ARC, but I have not found any reasonably priced uppers in stock. And the only barrels I found that I liked seemed to have less than an optimum twist for the ARC. 1:8 (Faxon) rather than 1:75 or faster. What barrels is anyone here having good luck with, and in what twist rate?

I wanted a long barrel for my 6mm ARC. EABCO may not be widely known for their barrels, but I had previous success with their T/C Encore barrels. The 24-inch barrel I linked to above is 1:7.5 twist. Liking it so far.

Legionnaire said:

I wanted a long barrel for my 6mm ARC. EABCO may not be widely known for their barrels, but I had previous success with their T/C Encore barrels. The 24-inch barrel I linked to above is 1:7.5 twist. Liking it so far.

Click to expand...

I will give them a look. Usually when I commit to an AR caliber, I build several models with different barrel lengths, especially with long range target calibers such as the 6mm ARC. I certainly plan to build a couple 24" ones, but as with my 6.5 Grendel ARs, I will likely build a few from 10.5 to 24."

Does anyone know how the 6mm ARC does with shorter barrels? My 6.5 Grendel does great with short barrels, but I never built any .224 Valkyrie uppers shorter than 18" because on paper the ballistics don't seem to be suited to shorter barrels.
citizenconn

citizenconn said:

Does anyone know how the 6mm ARC does with shorter barrels? My 6.5 Grendel does great with short barrels, but I never built any .224 Valkyrie uppers shorter than 18" because on paper the ballistics don't seem to be suited to shorter barrels.

Click to expand...

Same same… the 6 ARC has a lower bore:case volume ratio, lower expansion ratio, so it benefits more from having longer barrels than say, 6.5 Grendel or 300blk. I’ve seen data as short as 11.5”, and the performance remains quite good. Slower, for sure, but still very potent for applications where an SBR might be appropriate. I’m intending to rebarrel one of my deer hunting uppers to 6 ARC - it’s a 10.5” 6.8 SPC currently, and I believe I’ll be going like for like with a 10.5” 6 ARC - I kicked around a 12”, but I simply enjoy the handing of 10.5’s. Only caveat which could change my mind will be if SiCo tells me 12” is the minimum for 6 ARC with my Omega.