For Things That Go Bump in the Night- Suppressed 300 Blackout SBR Custom Build
ETA: FYI, if you are using Tapatalk and are not seeing my parts list, Tapatalk is cutting out 3/4ths of my post and I have no idea why. If you are seeing the parts list, then it’s just messed up on my end...
A few of you guys that know me know about my "Rule of Commonality". It means my firearms will be in common calibers. Up until this build that has been 9mm, 5.56 and 7.62x51. All NATO rounds. All ammo in abundance. But after finally getting my AAC 762 SDN-6 can, the idea of having an SBR with the potential for really quiet operation became very appealing to me. Realizing the range limitations of subsonic 300 ammo, I still felt that I had a solid purpose for a weapon of this type in my defense plan. It's kind of crazy how I ended up with a BA Premium 8" 300BLK barrel, but it sort of magically morphed into that from a 16" Faxon Gunner 300BLK. That story for another time.
I also wanted to build this AR - as much as possible with existing parts, some of them used on my other builds, that I've broken down or were on AR's I no longer shot. From a price-point - this is a budget build. From a parts perspective, IMO, it is as good as any AR I've built.
Total out of pocket to get this SBR operational: $206. I had to pick up a 7" LaRue Tactical rail (thanks docsherm) and a AAC 51T Blackout 5/8x24 from Lanbo's Armory
Upper:
Upper Receiver: I believe this is an upper I picked up from AAC. It has a Mueller Industries forge mark on it. I had a few in my spare parts. They are either Aero, Colt, Vltor MUR-1A, or AAC. This definitely is not the Colt or Vltor and Aero usually has an "A" forge mark.
Barrel: Ballistic Advantage Premium 8" 300 Blackout: It's no secret these are some of my favorite barrels. My longer BA barrels are both subMOA barrels -very accurate. My other SBR barrels shoot as well as my Daniel Defense barrels. For the money, you're hard pressed to beat them.
BCG: LMT L7D3 (FA) BCG - Because I pretty much only use LMT L7D3's or their enhanced bolt carrier (L7Q3A) with standard LMT bolt. I believe they are are tough as nails and as well made as a BCG can be.
Charging Handle: Radian Raptor - formerly know as the Artist AXTS Raptor.
Gas Block: CMT JAG gas block (non-adjustable) with BA melonite pistol length gas tube
Muzzle Device: AAC Blackout 5/8 x 24 Muzzle Brake
Handguards: LaRue Tactical 7" rail. Because LaRue Tactical rails are the best quad rail in the world. 
BUIS: Daniel Defense (I like to run Precision Reflex fixed sights, but these are what I had on hand.)
Optic: EOTech EXPS-3
Lower:
Lower Receiver: Aero Precision standard stripped lower - They work
LPK: DSG Arms with DSG billet trigger guard, mag catch button, Radian Talon Short-Throw Ambi Safety Selector
Trigger: CMC 3.5 SS trigger. Its what I had on hand
Buffer System: Vltor A5 using an H0 buffer and Sprinco Green Spring
Buttstock: Magpul SL-S stock. These are growing on me and I had one on hand.
Pistol Grip: Hogue Overmolded w/ Beavertail
Addition Components:
- TRL-1S WML
- Troy Ambi Bolt Catch
- Boonie Packer Redi-Mag
- BCM Mod 3 Vertical Grip
- BFG VCAS padded sling
This SBR has a dedicated can - an AAC 762 SDN-6 (.30 cal can). Not that I have a lot to compare it to, but so far I'm very pleased with its performance. As an aside, my POI shift isn't as bad as I thought it would be.(This comment more geared towards when I shot my precision AR's with this can.) Since receiving this can (after waiting 547 days) I've bought another of the same, which is slated for my 308 precision AR.
Range time: Test fired suppressed and unsuppressed. Test fired 208gr and 220gr subsonic and 120gr super sonic ammo. Initially I was using an H2 buffer with the Green Spring, but the BCG would not lock back on empty mag while shooting unsuppressed subsonic ammo. I swapped out the H2 for a lighter H0 and the weapon worked as advertised - both unsuppressed subs, to suppressed supersonic. It runs flawlessly.
I mitigated gas blow-back by lining the horseshoe of the Raptor CH with black high temp RTV. (Thanks docsherm)
I zeroed it at 100 yds. At 100 yards the subsonic ammo doesn't have any drop. I'm able to hit my 8" consistently, and 6" plates 7/10.
I also was able to hit 8" plates and 3/10 hits on my 6" plate at 200 yards, but I had to use a magnifier. But I was pleased with that also.
Today at the PD range, at a distance of 50 yards, I was able to run some 5x5x5 drills that required running to each firing position, shooting into paper plates at 50m. I scored 15 hits all three iterations, under a timer in 24 seconds. I'm not saying that's bad or that's good. I think it's OK. A funny thing, was that we didn't get a good time until my last run because the can was too quiet and my LEO friend could't figure out why his timer wasn't working. With this setup, the barrel rise was almost unnoticeable, and I was able to squeeze off the 5 rounds pretty quickly.
So bottom line up front - I'm very, very happy with the build. I believe it will fill the purpose for which it was built perfectly. Once I got the right buffer in it, she ran like the proverbial top and I have experienced zero malfunctions. It is a better CQB rifle than I anticipated, because my follow-on shots are much faster and my groupings are very tight. The HD ammo I use (Hornady Black 208gr Subsonic) peels back like an onion and would create a rather large wound channel/cavity. So it fits that purpose for me perfectly, plus on top being much more quiet than my 9mm and especially a 5.56.
Pics:
Not my best job, but it works.
Last edited by RobertTheTexan; 01-13-18 at 04:24.
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