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ChrisBrooklyn
12-09-2013, 5:56 AM
Hey all. In about to purchase an upper for my pistol build. Can't decide if I want to pull the trigger on a 300 blackout or a standard 5.56. All my other ars are 5.56 so for ammos sake it seems the best bet. But the more I read it seems that 300 is better suited to the shorter barrel. I plan on getting a 10.5 in barrel either way. I like the look and feel of that length for pistols.

m16
12-09-2013, 6:23 AM
I'm in the same boat.

Having several 5.56 rifles in the safe already, I decided to put together a 300BLK pistol using my last 80% receiver.

I'm using a Rainier Arms barrel with a 1:10" twist since I won't be shooting subs.

davidb
12-09-2013, 3:09 PM
im about to build a pistol and decided on 5.56 because ive got plenty of 5.56 mags and ammo and dont want to stock up on 300 mags+ammo

that being said if i had a reloader id probably go for 300 blk because from what ive read it works great for pistols, and its always fun to have something different

m16
12-09-2013, 3:16 PM
300 BLK takes 5.56 magazines.

technique
12-09-2013, 3:16 PM
I have hard use SBRs in both calibers.
You're fine with a 10.3/10.5, 5.56 pistol.

I prefer 300blk. With a short gun.


By the way, 300 and 5.56 mags are one in the same, davidb

davidb
12-09-2013, 3:22 PM
ah didnt know that thanks, that makes the decision a little easier, if ammo cost isnt an issue id definitly go 300 then

gun toting monkeyboy
12-09-2013, 3:36 PM
See, I like the 6.8 for short barrels. That is what it was designed for. I know that it isn't as trendy as the .300 is now, but it might be something for you to look into. 5.56 is nice if you don't want to deal with reloading or finding less common ammo. But its performance does suffer when used in these shorter barrels. It doesn't magically turn into a very loud .22 WMR, but you don't get anywhere near the performance that you do out of a 16 or 20 inch barrel.

-Mb

G38xOC
12-09-2013, 4:34 PM
I went with 223 only cuz , Im done reloading diff calibers .thought really hard abt going with 300tho .. at the end , just weren't ready to invest in dies..new powder..bullets..
Maybe later

Eljay
12-09-2013, 6:17 PM
I went 300 BLK and I like 300 BLK so much now I want a rifle in that caliber. It kind of never ends.

I don't know if you've ever shot a .223 AR Pistol but there's a ton of wasted energy. They're really loud but the actual ballistics are kind of sad, and you'll get reliability issues with the shorter length. So then you end up with an 11" barrel or something so it will actually run, which is kind of awkward. I'd really rather go with an 8" barrel and have it be reliable and actually use the energy of the cartridge.

The only issue is that if you don't reload then you'll be reduced to buying a case from Freedom Munitions when they do a run (about once a month) for 60 cents/round or you can wait until you can score some Remington. If you do reload 300 BLK's a great caliber for that. You just resize and trim some .223 brass, get a .308 bullet, and you're done. Nothing exotic about it. There's a thread about using cheap plated bullets at 11 cents/round. You can even cast 220gr bullets and make subsonic rounds - you have a lot of options.

technique
12-09-2013, 6:43 PM
I use Missouri 247gr. cast bullets. I get them for $32 per 250qty. They work well.

ChrisBrooklyn
12-10-2013, 12:11 AM
I like the idea of send +200 grain projectiles out of the ar platform. I think I'm gonna do it. For 300 is 10.5 or 9 best? I don't want to worry about reliability.

hawaii five-0
12-10-2013, 4:24 AM
Both lengths are reliable. AAC developed the cartridge, and they sell a 9 inch version

technique
12-10-2013, 5:26 AM
I run the Remington/AAC 9in. Upper.

I've never run sub in that gun unsuppressed, now that I think about it.
It has run flawlessly for me otherwise.

I've run BLK as short as 7in. and 8.5in. I've run 10.5in and 11.5in too. I ended up sticking with the 9in. mostly because I like that upper configuration but also because anything longer didn't prove to be any better from 0-300m.

Mine is 1:7 and seems to handle subs and super just fine, again from 0-300m.
If you wanna shoot mostly super, maybe the 1:10 barrels are better for that.

Eljay
12-10-2013, 6:11 AM
The AAC uppers (which are excellent) are tuned so they'll run subs unsurpassed. Noveske seems to assume you'll have a suppressor. I don't know about other companies.

I'm sure the Missouri cast work fine but if you cast yourself there's maybe 5 cents of lead in there even if you're buying alloy from rotometals.

technique
12-10-2013, 6:25 AM
Noveske is one of the only companies that has it right with 14.5/16in barrels. They use the pistol gas and they cycle subs unsuppressed.

CMMG is also doing the same, but it wasn't cycling subs.

mif_slim
12-10-2013, 7:38 AM
Ive used ***(alpha shooting sports! Not actual a**, lol) and their 10.5 is ram on pistol gas. I can run subs at 230gr without suppressor and able to cycle the bolt completely. Also run boarder line sub/sonic with 165gr with no issues.

Like tech I use cast bullets, which I cast myself so I save a ton on $. If you reload, go for 300aac. Great round.