[Bllade]

Ok, I was wondering what do you think is the most common or desireable caliber for an AR platform not of the standard 5.56/.223.
.308, 6.5, .45, 9mm... what one would you like to have and why?

As for me a 45acp would be nice since I have 10's of thousands of rounds available that I will never go through just with my handguns....

 

[1uglyfox]

.308, you can buy it anywhere. That's why I own one. And of you can't shoot all your .45 ACP, I'd be willing to lend a hand disposing of all that "evil".

 

[GuyMontag]

Real question is what are you looking for in the rifle?

I've a buddy who isn't into rifles, but loves his handguns and the 9mm was a good fit for his needs and reloading budget.

His situation was a bit like yours, except you're flush with .45 ammo, he's a 9mm guy.

Would I want a 9mm upper, no, but my friend couldn't be happier with his 9mm upper.

He realizes his AR is not some super-sniper rig, but that's not what he wanted in the platform.

6.5 Creedmoor is what's going on my next large frame AR, great ballistics and a helluva cartridge.

 

[cgrutt]

Would love to build an AR in .308 but don't you need to step up to the AR10 receiver?

Staying within AR15 6.8 SPC was my first choice. Very similar to .223/5.56 with a little more punch. Ammo seems to be readily available without having to reload, but reloading also opens up a lot of options. Only difference from standard configuration is bolt, barrel and mag.

Heard the 6.5 is a round better left to experienced reloaders.

.204 Ruger is on my watchlist for a future build.

 

[dsdmmat]

Ok, I was wondering what do you think is the most common or desireable caliber for an AR platform not of the standard 5.56/.223.
.308, 6.5, .45, 9mm... what one would you like to have and why?

As for me a 45acp would be nice since I have 10's of thousands of rounds available that I will never go through just with my handguns....

I try to stick to military/Law Enforcement calibers, I say try because I do not and will not own a 9mm. I do this for commonality if for no other reason. .556 and 308 are the primary uppers in my safe.

I do have a 5.7 upper just for grins, it was my attempt to get my ol lady into shooting the EBR (which failed miserably). I have been trying to find a place to make some specialty lowers for some of my pistol magazines these would be matched with uppers in pistol calibers that I own so there is commonality in magazines as well as calibers for my double stacked 1911s and carbines (easier to carry 12 of one mag type than 6 of two). If I can find a place to make me what I desire, I will have ARs in calibers 45 ACP, 10mm, and 38 Super for Pistol/Carbine compatability.

Would love to build an AR in .308 but don't you need to step up to the AR10 receiver?

yes

 

[SierraOne]

I just went through this myself and after watching some youtube videos and forum reviews I ended up going for
the 300 Blackout upper.

I have not even received the upper yet. So, at this time I have no experience other than reading about it.

I liked the fact that it uses the same mags and BCG which is a plus to me since I don't have to invest in replacement
parts and I get to use my trusty ol' pre bans! The only difference is the barrel which can be bought and assembled
on a standard upper receiver. The downside for this caliber is that it is relatively new and the ammo can be scarce to find locally.

 

[LDD]

.308 doesn't fit in your standard AR15 magwell, so that's out (unless you get a single-shot upper).

Statistically speaking, after 5.56 is probably .22lr, then 9mm in terms of overall popularity. .45 and .40 not so much.

7.62x39 would have been a popular round if someone mad decent magazines for it. Looking for preban mags though? Not worth it.

5.45x39 and 5,7x28 both have ammo issues, though mags aren't hard to get (in free states).

6.5 and 6.8 are specialty cartridges. They outperform the 5.56 but unless you're invested into reloading, you're going to pay a bit to play that game.

.300 BLK is the new hot item, but for all the talk, I see very few people actually owning them and the ammo isn't all that available either. Additionally, unless you run your .300 BLK upper with a suppressor, you're not getting the full advantage of the cartridge (again a strike against it in ban states).

5.56 because it is common and standard

9mm for the same, and you can still use it in ranges that do not allow centerfire rifle calibers.

.22lr because it's about as cheap as shooting any smokless powder ammunition will ever be.

Anything else, be prepared to see a rise in support costs (the ammo itself or magazines to feed your ammo from).

 

[ODgreenAK]

I have 5.45x39 and 5.7 uppers and love both of them.

 

[GuyMontag]

.300 BLK is the new hot item, but for all the talk, I see very few people actually owning them and the ammo isn't all that available either. Additionally, unless you run your .300 BLK upper with a suppressor, you're not getting the full advantage of the cartridge (again a strike against it in ban states).

No suppressors in NY, which makes the appeal of a .300 BLK limited in my opinion as well.

 

[Mike_in_MD]

In my area, 9mm carbines are common because we can get suppressors and also make SBR's. Some of the clubs are having steel plate shoots and they have pistol caliber carbine side matches, so the 9mm is also fun there. The indoor range five minutes from me also allows pistol caliber rifles/carbines but not 5.56.

The .300 BLK has also gained a footing here, again because of the availability of NFA toys here. At least two shops near me stock uppers and ammo for that round.

As a .22 rimfire fan, I think everyone should have an upper or dedicated .22 AR rifle.

 

[Catfish787]

Not sure what your use is, but .308, 300 AAC Blackout, and 6.8 SPC are all excellent calibers.

6.8 SPC, for example, has the stopping power of a 7.62x39mm with the accuracy of a 5.56mm. Hopefully the military switches to this round because If I was a soldier right now, I would not be too happy with the 5.56mm. I'd much rather have the 6.8SPC.

 

[BUCKrub91]

probably 6.8.. i dont count the .308 cause its not the same platform

 

[groovy mike]

308 and 50 BMG

 

[Cossey]

For the basic AR15 lower receiver, I don't know if I'll do anything other than 5.56 again. It's a great round for what anyone on here will use it for, for the most part. There's tons of QUALITY surplus ammo for it (meaning brass, reloadable, and clean firing), and with the hundreds of different bullet weights and designs, I'd feel you'd be hard pressed to find a better all-around round in terms of recoil, performance, ease to find, and price.

That being said, several non 5.56 calibers have piqued my interest over the years, even though I legitimately have no use for them other than the "why not" factor. I don't hunt, all I do is shoot paper. 50 Beowulf looks awesome to me just because it's a huge effing round for an AR15 receiver. 6.8 SPC is nice for some people, as are 6.5 Grendel, 7.62x40, etc...

My next AR will be another .308 platform though. I just love the AR platform too much lol.

 

[cgrutt]

6.8 SPC, for example, has the stopping power of a 7.62x39mm with the accuracy of a 5.56mm. Hopefully the military switches to this round because If I was a soldier right now, I would not be too happy with the 5.56mm. I'd much rather have the 6.8SPC.

I have a 6.8 and love it. That said, when I go to training classes the 5.56 is my goto gun. I'm not military, but plenty of BG put down with 5.56. If I'd have to hump ammo, I'd also prefer to hump 5.56 over 6.8. Note you only get 25 6.8 rounds in a standard 30 round 5.56 mag. That's almost 20% more shots per mag than you get with a 6.8. Don't get me wrong, 6.8 is a great round but both have their uses.

 

[Catfish787]

I have a 6.8 and love it. That said, when I go to training classes the 5.56 is my goto gun. I'm not military, but plenty of BG put down with 5.56. If I'd have to hump ammo, I'd also prefer to hump 5.56 over 6.8. Note you only get 25 6.8 rounds in a standard 30 round 5.56 mag. That's almost 20% more shots per mag than you get with a 6.8. Don't get me wrong, 6.8 is a great round but both have their uses.

Yea... everyone has their own opinions I guess. I'm a big believer in stopping power and bullets weights though, cause I've seen practical relationships in the field (albeit a hutning field, not military) when shooting deer and wild boars with .223 vs. .308win. I'm one of those people who would rather carry heavier ammo if it meant more stopping power.

Good video to watch if you have time:

LWRC PSD Future Weapons - YouTube

 

[RennFab]

Next best drop in + caliber cartridge that's readily available off shelf is the 6.8 SPC. Handloads, 6.5BR seems to be the ticket. Those are just the easy ones. When you start getting into wildcat cartridges and loaded/fireforming the sky can really be the limit(given your wallet doesn't fold first.)

 

[digitalhippie]

I have 5.45x39 and 5.7 uppers and love both of them.

I love my 5.45

 

[timmyp]

.22 LR

By the way, I'm always interested in some free .45ACP if you're looking to lighten your stockpile. PM me for my address.

 

[Noodles]

I think the .300-221 Fireball Whisper Hush Blackout does have it's own appeal for a more serious reloader; heavy cast boolits maintain a low velocity at full power loads that'll still cycle. Can't say that about much else you're going to shoot from an AR. And you can throw some 110 grain soft-point rounds in the same upper moving at a good 2400 ft/s or so.

On the other side of the spectrum, the 6.5 allows the use of high-BC bullets. It's not far behind the .308, and can retain more energy at 600 yards than 150gr FMJ-BTs. It's nearly the same as a 6.5mmBR, with a bit more case capacity, and I've shot groups out of mine no bigger than the palm of my hand at 150 yards working up loads with bad glass.