I am by no means an expert on rifle assembly but my latest build has worked well since day one so I thought I'd share. I've built two AR's, one with a .223 Wylde chamber and now the 300 blackout. I smartly purchased a complete "factory" 308 AR as I've read too many horror stories on building one and quite frankly, it'd be hard to do my own build and beat the one I have now.
The 300 blackout I built has functioned with subs, supers, suppressed and unsuppressed and I just wanted to share the parts list as it has been mostly a success except for one issue that I'll get to in a bit. If the list helps others out, great! It is a Form 1 SBR and registered as such.
The basic components:
Faxon 10.5" Match stainless 416R nitrided barrel, 5R rifling, pistol length gas
Superlative Arms adjustable gas block
Rainier Arms titanium BCG with a POF roller cam pin
Odin Works adjustable buffer
OSS 762 Ti suppressor
Strike Industries flat wire spring
The lower is shared with a .223 upper which is also a Faxon match, 16" in length and uses a Rubber City Armory titanium BCG which is .1oz lighter than the Rainier. I chose the Rainier for the 300 blackout as the RCA was unobtanium at the time and I needed the BCG's to match in weight for function's sake. I upgraded the gas key so I could run the roller cam pin. RCA used to offer it as a turn-key package but they no longer do which sucks as they'd coat the key in their proprietary coating. I have that version for the .223 and would have loved to have had another but it wasn't in the cards. Doesn't appear Rainier is making their Ti BCG any more either. You can still get the RCA just without the POF roller cam pin.
I have to double check the Odin Works buffer but I believe I'm running two aluminum and one steel so it's fairly light. I don't have the weight off the top of my head but I can yank it out and weigh it.
After assembling the 300 Blackout and taking it out to the range to perform function checks, I dialed it in for supers, then subs and then dialed the gas back to the supers setting. Locks back on an empty mag for both and took me no time whatsoever.
Performance wise, with off the shelf S&B's I was able to get a slightly sub-MOA group with a 1-4 LVPO. I literally had no idea I'd done it until I checked the target. I've since gone with a Primary Arms 1-6 with the 300 Blk reticle. The other scope has far better glass but a .223 reticle and the PA keeps it simple.
To date, it's worked with a variety of supers and subs, mostly 110-125gr supers along with subs from 190 to 220 grain, factory loads. Shoots everything and I've had zero FTF's to date.
The one issue I've had is bullet setback with Hornady's 190 Sub-X and I'm currently chasing down that issue. Faxon is sending a new barrel as I'm also seeing striations, horizontal marks, on various bullets if I chamber them. They're all straight lines around a portion of the bullet's circumference along with a gouge near the case neck.
I also purchased a Rainier Arms 8.5" so we'll see how that functions with everything else in my setup. I did this due to the setback issue and it actually being in stock.
The OSS, being a flow through design is a big part of everything functioning the same when suppressed. It's stupid quiet with subs and other at the range usually laugh the first time they hear the rifle suppressed with subs.
The BCG still gets remarkably dirty with subs and I've debated going with a piston conversion kit. I've since been talked out of it as the current setup works. I did switch to an RCA bolt and firing pin as the coating seems to be better than the Rainier's coating, cleans up easier. I also have a JP enhanced which I haven't tried yet but will be used with the Rainier barrel.
I had started load development with 110gr. Vmax bullets and was seeing over 2200fps consistently with a medium powder load in the 10.5" barrel with suppressor attached.
The other non-function stuff consists of a VSeven G4 forged upper, American Defense manufacturing ambient lower, Smoke Composites hand guard and buffer tube. Using a Velocity 4-pound trigger. Charging handle is the Precision Reflex gas busters ambidextrous large latch charging handle. The VSeven upper is interference fit with the Faxon and Rainier barrels. Naked, without accessories and scope, it's 4.8 pounds with the Faxon barrel.
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