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Best long range ar15 caliber

Hey guys, im considering rebarreling a 20" 5.56 ar15 setup i have had for years and i want your opinion on what would be the most capable, accurate, long range caliber i could choose for this platform

it would eventually be suppressed (still waiting) and used occasionally to house one of my thermal scopes for night coyote hunting, but primarily will wear a day scope.

I currently use a 14.5" 6mm arc for night hunting that i love, so that round is certainly a consideration. interested to hear everyones thoughts. I would prefer to keep it around a 20" barrel but would go longer if needed.

My requirements listed by priority

1. long distance accuracy (400+)
2. flattest trajectory possible
3. ammo/reloading component availability (when things are "normal")

Thanks in advance
.300 Win Mag
 
The 223 isn’t really any flatter shooting at any distance (close or long) if you’re comparing apples to apples. Remember the 6mm can go down to 55gr or less if you want a short range varmint round, and in most apples to apples comparison it’ll achieve the same or faster speeds with a better b.c.

If it were me, I’d look into a 20”-24” 6mm ARC and make your 5.56 a 14.5”-16”. IMO that covers a lot more ground than the setups you have now.

with that said, the 6mm is good in all barrel lengths; even my 12.5” (earlier wildcat 6mm Grendel variant) is still easy to hit with at 600-700 yards and more, but the 24” does the same thing better.
FWIW, in my experience with 105gr loads in my 6mm arc variants, a 20” gains about 250 fps over a 12.5”, and a 24” about 100 fps more than that.

Also, if you’re loading for this - Leverevolution.
Currently sitting on varget, cfe-223, and h4350 for rifle powders...but always looking for whatever comes in to stock
 
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You may want to check out 6.5 Grendel ballistics. .264" diasmeter is the sweet sp[ot for flat trajectory and wind resistance. The Grendel is touted as a 400 yd. cartridge; 400 yds on game may be a stretch. The cartridge is very efficient; you can get 50% more power than a .223/5.56 cartridge for just a few more grains of powder. If you want more long range power, you'll have to move up to the heavier AR10 in cartridges like the 6.5 Creedmor and larger. Staying with the AR15, I would recommend the Grendel.
Not really. I like the 6.5 too but it’s not a “sweet spot” any more than any other caliber, just a different balance of one thing vs another. The 6mm versions of the same thing are MUCH flatter shooting at any range. Would you rather have a .530 G1 at 2450-2500 fps or the same .530 G1 at 2750-2850 fps? That’s the difference between the 6.5 and the 6.
 
Currently sitting on varget, cfe-223, and h4350 for rifle powders...but always looking for whatever comes in to stock
CFE223 is pretty close to Lever. Not quite as good, and IME not the same easy load development as Lever (find max, test for seating depth, and run it), but it’ll do. On the other hand, Lever is one of the few powders that’s readily available around here at the moment. If you want some, now’s the time to find it.

The barrel quality concern is valid, but personally I’d rather get what I really wanted in a good barrel and wait a little, than to compromise and get something different. Know anyone who can spin one up for you on a lathe? That’s been my route lately (although I do my own) since quality blanks are available in whatever caliber you want.
 
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243 wsm in a small frame AR. 1000 yards easy with sierra 95gr match bullets. Heavier bullets have better BC but will have difficulty fitting within mag length constraints.
That’d look a lot more attractive if there were any good options left on the market for bolts and barrel extensions. And of course ammo and brass.
 
.243 wsm has certainly crossed my mind but as stated before, not much available. The main problem I have with waiting is personally I feel we are at the beginning of the shortages if the obummer years are any kind of indicator
 
6.5 grendel. I have a barrel from Criterion. Took a whitetail at over 300 yards with American eagle OTM. The exit wound was about the size of a half dollar. Couldnt believe it. Ive read months worth on forums about grendels. From accuracy to SAAMI chambering. People say they are finicky in some aspects. However, ive never had a problem with mine, and ive taken it out to 500 yards with pretty damn good results.
 
Fiddynuts. Consider Satern cut rifling barrels in Estherville, IA. Very high quality product. They also offer button rifled barrels at less cost. https://www.saternbarrels.net.
This definitely appeals to me as I'm from iowa!

Yeah, well the four plus year wait time on a custom barrel won't. I finally gave up. IF they have what you want in stock, get it. If they don't pass. It does me all of jack shit that they can cut rifling to .01" or offer all these profiles and cuts if they can't deliver. Which they can't.

That said, my best rifle/best barrel is a 6.5G Satern that shoots a consistent .33MOA with 120gr. BT's.

My goto for cut rifling is Krieger, they won't let you down. Amazed at the quality of the one in my custom recce rifle I put together.

As for caliber, you won't beat 6.5G for all around bad assery in the AR platform, fact. There are faster, lighter and flatter but there isn't another combination like that which also puts targets on asses that I'm aware of. Hell, I liked it so much I put an SBR together in 6.5G but I gotta admit the .300BLK is a better option here.
 
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6.5 grendel would currently be out for me due to lack of ammo and reloading supplies.

So, criterion .223 match setup with matching bolt. Or faxon 6arc with generic type2 bolt and a little extra money towards the optic
 
People recommending 6.5 Grendel as a flat shooter? It’s a great LR cartridge for the AR15, but that’s one of the areas it loses easily to the others. For the ranges I’m seeing from OP (400-750) I’d go 6 ARC or 224 Valk shooting something like 75 ELDs instead of the 90-95 SMKs. I’m really hoping a 22 ARC is in the works down the line.
I have a 224 predator and use 65 grain nosler bt in it it’s almost sad what it does to a groudhog
 
So, criterion .223 match setup with matching bolt. Or faxon 6arc with generic type2 bolt and a little extra money towards the optic
I've sold both of my Faxon barrels due to inadequate accuracy. Definitely keeping my Criterions. Small sample size I know, but figured I'd share my experiences with barrels from both companies.
 
For everyone proposing a 6.5grendel.... Have you actually compared the ballistics of other cartridges?

I have a 30-30 in the safe, but I wouldn’t suggest it as the flattest deer hunting cartridge out to 300yds or the best long range hunting cartridge.
This.

I have a 6.5 Grendel, and it's a great cartridge, and I won't be casting it aside for 6mm ARC. But for what OP wants to do, a high BC 6mm or .243 caliber cartridge will be superior for long range precision work. And since OP already owns a 6mm ARC that shoots (relatively) fast & flat, 6.5 Grendel is a step in the wrong direction.

OP - SixFiveArms.com is expecting some 20" 6mm ARC barrels in February, made from Green Mountain blanks. At a price comparable to their Grendel barrels (well under $200), that should be a good option for you if you don't want to wait (or pay) for a custom made barrel.
 
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For everyone proposing a 6.5grendel....

Have you actually compared the ballistics of other cartridges?

I have a 30-30 in the safe, but I wouldn’t suggest it as the flattest deer hunting cartridge out to 300yds or the best long range hunting cartridge.

Agreed. I have six rifles chambered in 6.5 Grendel (4 ARs with 12.5", 16", 18", 20" barrels and 2 Howa Mini Actions with 20" barrels). It's not what he seeks.

I concur with 6mm ARC as the best suggestion. I just built a 22" 6mm ARC AR and next up I'll be rechambering one of the Howa Mini's as well.
 
Agreed. I have six rifles chambered in 6.5 Grendel (4 ARs with 12.5", 16", 18", 20" barrels and 2 Howa Mini Actions with 20" barrels). It's not what he seeks.

I concur with 6mm ARC as the best suggestion. I just built a 22" 6mm ARC AR and next up I'll be rechambering one of the Howa Mini's as well.

Yep. As we see all too often here, people recommend what they have because it validates their own choices, not because it’s the best answer for the question that was asked. The Grendel recommendations are a great example of that. It’s a fine cartridge and is capable at distance, but falls behind in comparison to it’s 6mm sibling, and the difference is pretty significant.

Owning multiple barrel lengths of all the above, I’d rather use the Grendel than the 5.56 at distance, but the 6mm is better than either one. Even my 12.5” 6mm is easier to hit with at distance than my 16” 5.56, by a big margin.
 
So as a scenario. If I were to up my barrel budget to $500 (preferably with a matching bolt)

And also became willing to wait 6-8 weeks

With the goal of having the most capable ar15 setup for hitting a prairie dog at 600yds

What would your barrel recommendations be?

Stick with RA ultramatch (18" .223) or woa shilen ratchet 20"(would need to get threaded)-

wait for a CLE 20" .223-

find a proof 18" 6arc, or order a criterion 20" 6arc?

Any better suggestions? I'm equally as capable to handload .223 or 6arc with equal components on hand for each (this is the reason my search has narrowed to these 2 cartriges)
 
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For parrie dog, 204 ruger all the way. Here is a bit of data on 204 vs 223 vs 6 arc. You could use a different bullet, but nothing is going to come close to that velocity advantage. It will blow around in the wind a bit more, buy nothing too crazy. 6 Arc would be the second choice, 223 is just outclassed by either of these other options.
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With a quick search, the 204 might be hard for me to find reloading components, kind of puts me in the same boat as other calibers mentioned.

In my situation I've narrowed it to these barrels in order. Preference leaning towards the arc as I think it will prove more versatile







Opinions on these options?
 
I'd go with the ARC and wouldn't settle for anything less than 20" for what you're wanting. Really there's not much reason to avoid just going with a 24" if you're looking for long range and things like prairie dogs. If the point is something compact that's different, but you've already got a 14.5"; might as well go for a big difference in barrel length instead of a small jump.

Or instead of 204 you can go 20 Tactical (simple reforming of 5.56 brass). Ballistics are about the same, I get 3950 with a 40gr Vmax over Lever from my 24". FYI most of the advice and recommendations about the 20 Tactical vs the Practical are complete crap and actually backwards. The Tactical is a very easy single pass forming through the Hornady FL dies, which are available if you look around and you don't have to spend $150+ on a Redding bushing die unless you want to. Mine shoots about the same with freshly formed brass as it does with once fired; excellent either way. I'm just using LC 19 brass, and it loads about the same whether it starts as 5.56 or 20 Tac.

IMO regardless which of the 20 cal variants you choose, 400 yards is about the limit in any kind of wind. Inside that it's a laser beam, but the little 20 cal is pretty small for reaching out further. Nearly zero recoil and reticle movement though so it's a lot of fun to shoot.
 
The 6ARC will give you some benefits with wind. If “I” was going with a 6ARC, I’d get a 20-22” or longer to get the most out of it. I’d just make sure you get a quality barrel that is known to shoot great.

With that said, I can hit the 4” plate at 500yds with my 18” 223wylde pretty consistently if the winds aren’t too switchy. If going 223wylde, the WOA or Rainier Ultramatch will both shoot great. Having owned several RA Ultramatch barrels, I’d expect them to shoot below 3/4moa, and closer to half moa with a good load.
 
When I decided to go 6.5g, 6mm arc wasn't much of a thing.

However the 6.5g will stay with me as a mid range msr tool.

Imho
 
My requirements listed by priority

1. long distance accuracy (400+)
2. flattest trajectory possible
3. ammo/reloading component availability (when things are "normal")

Thanks in advance
Really based on your criteria that's not a hard bar to get over. It ultimately depends on the end use and much more on ammo choices than anything. Bullets designed for hunting are not always best for other uses and bullets designed for target shooting are not always best for hunting. Bullet weight, velocity, barrel length, etc that whole combination gives you a ton of options. But again, that depends on what kind of things you will be shooting at.

400 yards is not at all that far when it comes to shooting. I was tempted to reply with what "I think" long range means but I am trying to stay within how you framed the question.

Really though bullet weight, velocity, bullet type, all those things are more ammo related than cartridge related so in my book (considering your idea of long range and mine are totally different), this actually comes back to doing ammo research more than it's about gun research.
 
Guess it's all a mute point at the moment.
Changed powders since out of 8208 .
No 6.5 bullets for good grendel loads.
No brass.
No primers.

No joy.

Saving 6.5g stock and shooting 223 for now.

Boaring !

Any you deplorables want to have a slingshot or speer chucking match ?
 
From what I can gather the shaw and faxon barrels are the only ones inside a 12 week wait that are 18" or over for the 6arc. Neither seem to be super well regarded.

After further research it appears .224 valkrie supplies and barrels are much more available, and this setup seems to provide a happy medium between a match .223 setup and a 6arc. I already have some .224 projectiles and potentially some powders that will work so that's a start

So with that being said I am heavily leaning to this RA ultramatch thats in stock and just ending this painful search

 
224 Valkyrie. Shoots flat - 1300 yards- ammo is available and cheaper than 223 right now. Rainier Arms match barrel is awesome 1/2 to 3/4 moa 100 yards - but it was made for long range and coyotes
This is where my thoughts are at
 
From what I can gather the shaw and faxon barrels are the only ones inside a 12 week wait that are 18" or over for the 6arc. Neither seem to be super well regarded.

After further research it appears .224 valkrie supplies and barrels are much more available, and this setup seems to provide a happy medium between a match .223 setup and a 6arc. I already have some .224 projectiles and potentially some powders that will work so that's a start

So with that being said I am heavily leaning to this RA ultramatch thats in stock and just ending this painful search


Having 2 of the RA 224’s, feed them H4895 and 80 eld’s!! Super shooters. They shoot the FGMM 80.5 factory load as well.
 
224 is a great option, I am running a criterion 22" barrel. It shoots great, and is a mid weight profile if you were looking for something a bit more handy and easier to cary. The Rainer arms is a great option as well, it will be up to you how far you are carrying it.
 
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....flip a coin and make a decision. The stated goal of 400+ can be satisfied by both .223/5.56 and 6MM bullets in multiple weights and bullet types, especially when being used for groundhogs as stated. More of the .243/6mm bullets will give wind advantages over majority of the .22 bullets at the 400+ distances. .224Valk reports indicate users have encountered more issues finding an accurate/acceptable load when compared to 6ARC reports (to date). Each caliber has reports of a handful of specific barrel makers that keep "off-the shelf stocks" that consistently receive favorable reviews by users (CLE, Rainier, Craddock, Criterion, WOA, Proof (steel & carbon) right out of the box with minimal load development involved, more so for the .223/5.56 as opposed to 6ARC, the 6ARC is still too "new".

You stated you have sufficient components to load for either caliber and have concerns about future availability, suggest you stick to these 2 calibers for now at least, pick one and proceed, keeping in mind how much of your component stock you will use up developing a load for whatever barrel you settle on.
 
Pulled the trigger on the RA ultramatch 20" .224 valk...I think it will fit my needs better than the .223 and current supply for supporting components is night and day better for the valk than the arc.

I appreciate everyone's input on this and I look forward to the build. I'll definitely throw a pic up once I get it cerakoted and assembled
 
How do the 88's do in that 224V?
Personal experience is great. They are one of the most forgiving bullets for 224 Valkyrie. 80 Eldms will do better if you can push them fast enough, but the attached video is my own experience. 224 Valk was the rifle on the left, small poofs. 7 WSM on the right, large poofs at 1000 yards. square plate is 10x10 or 12x12 for size. Sorry for all the mirage.

Load details: 88 eld m, StaBall 6.5, Starline case, CCI 400
Rifle: 22" Criterion 1:6.5 barrel, AR-15 platform, Vortex Razor LH 3-15x42 (older model, not the newer LHT).
 
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How do the 88's do in that 224V?
They shot really well and really bad. 3-4 in a 1/2” group and then a 2” flyer. It was maddening. After 2 weeks of chasing it I finally figured out the tips were randomly catching the face of the chamber and breaking when cycling. Rather than trying to fix it I just swapped to 90smks and never looked back.
 
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What are the details of the rifle/load to achieve 2830 with the 90s?
Had to look back at notes becaue I haven’t shot much lately.... it’s 2730 not 2830 my bad. We’ve got too many rifles to keep up with lol.
Rifle is a 22” X-Caliber built on a mega MKM. 26.9 2000MR.
 
Any quality National Match barrel or upper should meet your needs with a 77 smk. 77's go trans sonic around 750 yards in a 20 inch barrel. WOA barrels ($220)or uppers will keep you sub moa as will a Rock River Arms upper ($710 with bcg and charging handle(sold as the CMP Model)). Load 77's in the 2700 to 2750 ball park, MK262 equivalent.