Warning

 

Close
Confirm Action

Are you sure you wish to do this?

Cancel Confirm
AR15.COM
AR Sponsor
8/1/2013 7:43:48 AM EDT
I am trying to figure out what I need exactly to build an AR 15 SBR with an 8.5" barrel, 300 blackout. I currently have a bushmaster AR with a 16" barrel in 5.56 mm. I know I can use the lower from that, but am not sure what I need to build the upper? I am trying to save some money and opting not to buy a complete upper. Also, can I use the bolt carrier group from my current rifle?
8/1/2013 7:46:27 AM EDT
[#1]
Quoted:
I am trying to figure out what I need exactly to build an AR 15 SBR with an 8.5" barrel, 300 blackout. I currently have a bushmaster AR with a 16" barrel in 5.56 mm. I know I can use the lower from that, but am not sure what I need to build the upper? I am trying to save some money and opting not to buy a complete upper. Also, can I use the bolt carrier group from my current rifle?
View Quote


Same bolt group and everything,  the only difference between .300 BLK and 5.56 is the barrel.
You'll need an upper receiver, handguards, barrel, muzzle device (with whatever threads your .300 barrel has) and gas block/tube.

You ARE getting that thing engraved and registered on a form 1 before you build your SBR upper, right?  right?
8/1/2013 7:54:38 AM EDT
[#2]
Yes I am expecting the tax stamp any day now. Thanks for the help!
8/1/2013 7:57:29 AM EDT
[#3]
Buy a lower from your favorite manufacture. Form 1 it. Put a pistol buffer tube on it. Build your upper. Enjoy till stamp comes. Enjoy even more.
8/1/2013 7:59:30 AM EDT
[#4]
Quote History
Quoted:
Yes I am expecting the tax stamp any day now. Thanks for the help!
View Quote


Oh to be young and full of hope...
8/1/2013 9:42:32 AM EDT
[#5]
a barrel, a pistol length gas tube, and pistol length handguard. everything else will work
8/1/2013 10:10:59 AM EDT
[#6]
I would make a whole separate upper consisting of the upper, barrel (with gas block and tube, and flashhider, I would look at the Noveske KX3 Flaming Pig)), rail, and BUIS.  The charging handle and BCG will work out of your 5.56.  Midway had CMMG 8.5" barrel's in stock last week as well as 9" samson Rails (on sale for $119).
AR Sponsor