300 blackout upper for Colt 6920 223/556 lower

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NikatKimber

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I like having an adjustable gas block on a .300 blk, if you’re going to be shooting both subs and supers. Even with that, plug and play uppers. Some people run different buffers, but I haven’t had an issue with the standard buffer in my lower with the adjustable gas block.
 

Mad Professor

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I like my 300blks.
Your upper selection might determine you success. I have three. 9”, 12.5”, and a 16”. All were built with factory AAC uppers. All three will run factory subs and supers with or with suppressors and function great.

I’ve seen several others screw around with stuff trying to make them run. Port size, buffer combos, adjustable gas blocks. etc. The they have to change sometime when they go from supers to subs or run a suppressor. I just change magazines and keep going.
 

steelfingers

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I like my 300blks.
Your upper selection might determine you success. I have three. 9”, 12.5”, and a 16”. All were built with factory AAC uppers. All three will run factory subs and supers with or with suppressors and function great.

I’ve seen several others screw around with stuff trying to make them run. Port size, buffer combos, adjustable gas blocks. etc. The they have to change sometime when they go from supers to subs or run a suppressor. I just change magazines and keep going.
I'm thinking about the 16" but want a complete upper with a quality barrel ready to drop in
 

steelfingers

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Want to bump this up for more suggestions. People here with suggestions I can trust so where to buy, brand, barrel and approximate cost for complete upper is appreciated. Not wanting anything that has to be adjusted just dropped in
16" barrel.
 

kirk1978

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I ordered a 300bl upper from Moriarti and it exceeded my expectations, is a tack driver at 100 yards (haven't had a chance to stretch it out beyond that). I know nothing about Moriarti, they may be junk for all I know but I've had great luck with the one I got from them.
 

k4ylr

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7.62x39 will offer you similar ballistics for much cheaper ammo. If you're not running a can, it's even more cost effective since shooting 300blk subs would be pointless. A 16" pistol gas should run just about everything

If you want parts parity, get 300blk since you can use standard AR mags and 5.56 BCGs are relatively inexpensive.

You'll have to hunt around for an assembled upper if you're not looking to build.

Then there's 6.5Grendel or 6.8spc if you're feeling really froggy.
 

steelfingers

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7.62x39 will offer you similar ballistics for much cheaper ammo. If you're not running a can, it's even more cost effective since shooting 300blk subs would be pointless. A 16" pistol gas should run just about everything

If you want parts parity, get 300blk since you can use standard AR mags and 5.56 BCGs are relatively inexpensive.

You'll have to hunt around for an assembled upper if you're not looking to build.

Then there's 6.5Grendel or 6.8spc if you're feeling really froggy.
Have a 7.62x39 in my AK. Sorta want the 300 bo. Complete upper prefered but will do a build if I have to. Never did a build and a bit iffy of trying it. Even thought about waiting till Wanamakers to look for a completed upper or all the parts for a build.
 

lasher

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not to start a fracas, but if given a BO i would instantly remove the barrel and put something in that would shoot a tad flatter and put more energy on target. now, if i were clearing an 8x10 room i'd want a suppressed BO, that's what it was made to do. but might be less dangerous to just flip in a M26 frag (if they still make that one)
 

beastep

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Im a big fan of the BO. Get one with pistol gas and has the largest gas hole you can find. May have to run an adjustable gas block though. Easy enough to do though. I run BCA because Im poor and they seem solid quality. I have a 300 BO BCA barrel that works well.
 

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