.300 blackout upper build checklist...

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MrWesson

New member
I'll start by saying i've never done an upper build and slightly confused on what i'll need and want to make sure I don't miss anything.

.300 barrel
Stripped upper
BCG
Rail
Gas block/tube
Ejection port cover
Charging handle

I have all the tools needed and have broken down my current upper a few times so i'm familiar with the process(its been awhile though).

I'm weighing buying vs building as I already own a couple of free float rails and supply is pretty dry right now for complete .300 uppers... This would be a budget build for sure(under $350 for upper).
 
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powrguy

Moderator
300 blackout upper build

My experience was with a pistol gas system on a carbine length barrel. NOT good....had case bases being torn on ejection, and would suggest you consider an adjustable gas block from the git=go....I wound up putting an adjustable gas block on mine, and thus was able to cure the ejection over-pressure.

Mine was a flat-top standard carbine setup, shooting supersonic reloads only. I tested several bullet/powder/primer combos, and was able to tune the gas system for best performance.


Just my .02 here; I'm not a competition shooter or expert on this, but have built my own AR's.
 
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pwalston25

New member
Looks like you've got everything you need. A couple tips that I can give, make sure to properly season the threads on the receiver and use some good mil spec grease around the barrel extension and on the receiver threads. There are plenty of good videos online if you need help.
 
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johnwilliamson062

Moderator
I've been looking at PSA's daily deals the last few weeks and they have run a couple decent deals on 300BO pistol uppers. I think they had one 10.5 also. I'd subscribe to their daily deal e-mail if I were you. I'm keeping my eye out for a nitrided barrel 16" in either 556 or 300 BO.
 
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berettaprofessor

New member
u. I'm keeping my eye out for a nitrided barrel 16" in either 556 or 300 BO.
Click to expand...

I bought a 16" 300 AAC nitrided upper from m4broker.com in November. $329 complete and it's been flawless for both supersonic and subsonic reloads. Very happy with that purchase.
 
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Ibmikey

New member
Depends on barrel length and supersonic vs subsonic, or both, as to the gas system. For short barrels definitely go with a pistol gas, mine works flawlessly with supersonic (i am not into subsonic) my carbine gas system on a 16" Rainier SS barrel also provides me with a reliable scoped AR. Also in the rack is a AAC Handi Rifle in 300 BO that is the neatest short range Texas hog hunter going. Love the 300 Blackout for shooting and reloading!
 
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MrWesson

New member
Can't wait to be able to cast my own bullets for .300 and not to mention less powder charge per round..

I want a rifle length as I don't want a pistol and don't want to play the SBR game. I plan on swapping upppers on my current lower until I source a dedicated lower for the .300.

I'm keeping my eye out but they seem much more common in pistol length vs carbine.
 
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stagpanther

New member
If you get a stripped lower and start with a pistol build--you get the best of both worlds--pistol and carbine since you can swap uppers. I don't think barrels over 10.5 gain you all that much in performance. I can tell you tha the 7.5" 300 BO pistol I recently put together is AWESOME--anyone who hasn't tried one--should! : )
 
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superspirit

New member
I've got a PSA 16" upper I bought a year or two back, it has a pistol gas system and has cycled subs and supers just fine. I would highly recommend it.
 
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