Building a lower for an SBR what do I need to know?

[NTXshooter]

I want to build an SBR in 300 Blackout. I'm going to build the lower and build the upper once I have the stamp. What's different from a standard carbine? Heavier buffer?

[98Z5V]

What's different from a standard carbine? Heavier buffer?

 

Not necessarily.  There's literally ONE part that's different than any standard AR-15  = the barrel.  I built Dawn Marie's 14.5" 300BLK rifle and started it with a standard carbine buffer.  It's a 14.5" carbine gas setup, I load the bullets with 150gr projos and a little hot. I felt I could soften it up a little for her, so I added an H2 buffer to it.  Shot great before, shoots a little better for her now, more controllable.

 

I'd say start with a standard buffer if you want, see how it does, and move to an H or H2 buffer later if you feel the need.  .

[shibiwan]

Well, if it's a 14.5 it's easy to "legalize" by pinning on a muzzle device of the right length without going through the NFA hullabaloo. I suppose NTX is looking for an even shorter setup.

 

For the 300 BLK build, I'd recommend a pistol length gas system with as light a buffer as possible. Go light on the BCG too if you can. Going this route (reduced weight reciprocating components) makes the 300BLK rifle more reliable for low-powered subsonic rounds, and you should be able to switch between supersonic and subsonic rounds (both firing unsuppressed) without futzing with anything.

 

I love my 300 BLK setup. Shoots like clockwork and recoil is like a .22LR!!

Edited May 24, 2014 by shibiwan

[unforgiven]

"What you need to know" don't shoot left handed or you'r face becomes the shell deflector.Just sayin.

[NTXshooter]

Thanks for the info. Headed to the gun show today to look for parts. Unfortunately, I'm a lefty. That's why I will never buy a slick side upper.

[unforgiven]

What I notice from having shot a SBR in Mass. is that the case ejects sharper to the rear almost 5:00 position.The upper was not slick side.I'll ask brother Ron to make sure later this morning.As a lefty myself all the other rifle's in mid-lenght and rifle-length gas eject more to the 4:00 position.I think the extream rearward ejection of case is the nature of the beast for SBR. <dontknow>

Edited May 24, 2014 by unforgiven

[NTXshooter]

Good to know. That could be a rude awakening to get a face full of hot brass.

[unforgiven]

Yea,it was a bit of a distraction.

[Robocop1051]

RRA just had a run of lefty uppers. STAG still puts out theirs every once in awhile.

If you're building a dedicated SBR, you might as well start in the right (or in your case, left) direction.

If you can grab an upper receiver and BCG, you can sit on those parts while you wait on your stamp. Finding them parts isn't an easy task... just ask Edgecrusher.

[unforgiven]

RRA lefty only works with the lefty lower.Stag has a lefty,then change barrel and cut down.American spirit might have a lefty.Talked to brother Ron and his SBR's had a shell deflector on them.Or get a righty and improvise a shell deflector.Good luck brother NTX.

[Rsquared]

Hey Tex. Stag is showing lefty upper receivers and bolt carrier's as in stock. Just to let you know. Can't get on American Spirit's sight right now...it appears to be down. As Robo said, start gathering parts while you wait for the stamp. They may evaporate from time to time.

 

What kind of barrel length are you looking for? Mine is a 10.5" Noveske barrel with a pistol length gas system. It'll eat up any kind of round I've fed to it so far. From the 110's supersonic, to the 220's subsonic (suppressed and unsuppressed). Here's an example of the overall length of mine. Keep in mind that I swapped the stocks out from a MOE to an ACS in between the pic taken. The can (AAC 762-SD) only adds about 7 inches to the OAL. My AAC SDN-6 adds about an inch or so less.

 

 

[edgecrusher]

Get the Stag stuff while it's in stock! I built my wife a lefty 5.56 rifle with their upper and lefty specific bcg, they were out of stock for nearly two years. Made my dad but the same just in case, as he isn't in a rush but those are the hard to find bits

[NTXshooter]

Rsquared, I'm looking at a 10.5" barrel or there abouts. How does it feel with the SDN-6? How do you like the that can? That is one of the cans on my short list.

Thanks for the heads up on the Stag stuff. I need to go place my order.

[Rsquared]

I describe the suppressed 300 BLK as "Hollywood quiet". Running sub-sonic rounds with the can attached, you'll hear the action of the rifle and the impacts on the berm more than the bang of the round going off.

[NTXshooter]

How does the balance feel? Also, does the barrel extension have to be different for left hand?

[Rsquared]

Nope. Barrel extension will be the same regardless. Just the carrier and upper need to be different. Balance on mine is just fine. She's pretty lightweight overall. And you don't have to take my word for it. I thought that Robo was gonna steal the thing from me once he started playing with it. Though I think he preferred the MK18. He was down right horny for that thing. Once he cleaned it that is. <lmao>

But that's another story.

[Robocop1051]

That Mk18 was pure sex for me. So dirty I damn near had to mortar it loose... only to make her extra dirty again.

Daniel Defense makes an awesome weapon. I'm especially impressed with their CHF barrels. The 10.3" seemed to be the sweet spot for me, although I think I could go to 11.5" without noticing much difference.

Edited May 26, 2014 by Robocop1051

[NTXshooter]

Thanks for the heads up on the Stag parts.  Now have an Upper and BCG ordered.  I am itching to pull the trigger on a can.  Any recommendations on a dealer?

[Robocop1051]

You know.... If you only want to buy and wait for one stamp... I think it was Spikes that sold a 9" 300Blk barrel with a suppressor welded to the end. The combo actually measures OAL as a 16.25" barrel, so you only need a suppressor stamp.

You won't be able to swap the suppressor between rifles, but you'd still have one badass machine on your hands.

[Robocop1051]

I guess if you wanted, just buy any direct mount suppressor, and have someone weld it to the barrel of your choice... just remember that most suppressors disassemble from the rear. You'd need one that disassembled from the front, to maintain that OAL of +16".

[NTXshooter]

I'm lookin  for a QD unit because I want to be able to switch the suppressor between rifles.  .300 when it is at home,.308 when I'm hunting, both of those  along with .556 and 6.8 when I'm at the range. 

[Magwa]

AAC-762-sdn-6 is the bad boy you want and a AAC 51T-Brakeout flash hider /adapter

[Robocop1051]

AAC-762-sdn-6 is the bad boy you want and a AAC 51T-Brakeout flash hider /adapter

I agree with the suppressor, but this is a better brake/adapter...

http://www.midwayusa.com/product/870752/advanced-armament-co-aac-blackout-muzzle-brake-51-tooth-ratchet-suppressor-mount-762mm-ar-10-lr-308-5-8-24-thread-steel-matte

The brake acts as the first two baffles of the suppressor. This increases the lifespan of the can... it's also one hellofa muzzle device!

[Rsquared]

Yep. That's a good one too. Trust me....the people to either side of me at the range hate me. <lmao>

[NTXshooter]

The SDN-6 is has a great reputation. I was also looking at the Thunder Beast 30BAS and YHM titanium Phantom QD. The 30 BAS and Phantom are about 4 oz. lighter.