300 blkout build questions

[TrickyNicky]

I've decided that I want to build a 300blk carbine to add some flavor to the AR stable.

I want to go with a carbine as I just can't seem to get into pistols and don't really want to go through the SBR process for right now.

My first question is regarding barrel length, I've heard that the standard 16" barrel doesn't do the round any favors and that shorter barrels are where the round really shines. With that said I have two options, buy a 16" barrel and run with it, or buy a shorter barrel and pin/weld a brake or KX3. I'd really rather go with a 16" barrel and be done with it, but if it will even theoretically help performance I could also see myself going the other route. Not sure if the 2-3" really makes any difference one way or the next?

Most of the barrels I'm considering are either 1 in 7" or 1 in 8" twist. I plan on shooting primarily without a suppressor but plan on shooting a mix of sub and supersonics. I may go with a can at some point but that's way into the future. Would either twist be preferred to the other with that in mind? I'm thinking it should be about the same but I want to make sure that I'm not setting myself up for baffle strikes in the future or anything.

Lastly, I'm planning on using an adjustable gas block, this should help me put some back pressure on the system to keep subsonics cycling without a can correct?

This is the one I'm considering most ATM, seems like a good value for what you get.
http://www.midwayusa.com/product/211944/ar-stoner-barrel-ar-15-300-aac-blackout-medium-contour-1-in-8-twist-16-stainless-steel


I'm also considering this one as well.
http://www.midwayusa.com/product/680713/cmmg-barrel-ar-15-300-aac-blackout-1-in-7-twist-16-carbine-gas-port-wasp-melonite-finished-chrome-moly-matte-pre-ban


Any thoughts or recommendations welcome, even those telling me to suck it up and build a damn pistol already.

[RED333]

I will let Dolomite chime in. He has done a LOT with this caliber.

I am getting the parts up as well for a 300, I am looking at this barrel.

http://www.midwayusa.com/product/311028/ar-stoner-barrel-ar-15-300-aac-blackout-lightweight-contour-1-in-8-twist-16-stainless-steel?cm_vc=subv1211944

Casting for this caliber, I was told to try and get a 1 x 10 twist, just can not find one.

[TrickyNicky]

Yup I'm waiting for G to give some advice as well.

I'm not worrying about casting just yet as I don't yet reload none the less cast. I looked at the light profile barrel as well, might go with that instead still, IDK.

[Lumber_Jack]

I would just go with the 16" it works just fine.  You gain about 20fps for every inch of barrel length so you are actually gaining a small amount.  The argument is that you dont loose much going all the way down to 8" or even shorter.  

 

1:8 is perfectly fine for most weights up to 220 grain, if you go heavier I'd probably get a 1:7 barrel.  Id buy either if the price is best, both will work fine

 

adjustable gas block is a great asset.  

 

Carbine length gas system will work fine for all supersonic ammo, and may work with subsonic but may not be reliable.  If you want the best of both worlds Id get a 16" barrel with a pistol length gas system.  Google Ron Williams Xtreme, he'll turn you a barrel for about $225

 

email rmwxtreme@verizon.net

 

If I were going to buy and off the shelf barrel Id buy one from Alpha Shooting Sports, good prices.  I have one in 10.5".  Appears they have 2 16" carbine gas in-stock

 

http://www.shop.ar15hardware.com/300-Black-Out_c44.htm

 

Or buy one from Rainier Arms

 

https://www.rainierarms.com/?page=shop/detail&product_id=3385

 

 

Ive heard mixed reports on the AR Stoner barrels so I personally would steer clear of them.  Some gas ports were misaligned, may have fixed the problem but there are better options for the same or less money

Edited December 30, 2013 by Lumber_Jack

[TNMTBik3r]

Following...planning on a unsuppressed 300 blackout build this spring to use for deer hunting.

[Dolomite_supafly]

LumberJack said it perfectly.

I will reiterate that a pistol length gas system is a must for reliable subsonic function. And a pistol length gas system with a 16" barrel opens up all kinds of powders for reloading.

If you want, give me a call and we can figure out what you need.

[TrickyNicky]

" If you want the best of both worlds Id get a 16" barrel with a pistol length gas system."


CMMG makes one,
http://www.midwayusa.com/product/657614/cmmg-barrel-ar-15-300-aac-blackout-1-in-7-twist-16-pistol-gas-port-wasp-melonite-finished-chrome-moly-matte-pre-ban

But they caution not to run supersonics with that configuration?

"•Suitable for use with Subsonic loads, either Suppressed or Unsuppressed
•Use of Supersonic loads is NOT recommended with Pistol Gas Port Location"

Maybe that's just them?

[Lumber_Jack]

Yeah I'm not sure what CMMG claims that. Also note the gas block seat is .936" so finding a gas block might be difficult. And it might not fit under some free float rails If you want a pistol length gas on a 16" you have two good options. 1) wait and find a Noveske for $455 2) call Ron Williams Edited December 30, 2013 by Lumber_Jack

[mikegideon]

" If you want the best of both worlds Id get a 16" barrel with a pistol length gas system."


CMMG makes one,
http://www.midwayusa.com/product/657614/cmmg-barrel-ar-15-300-aac-blackout-1-in-7-twist-16-pistol-gas-port-wasp-melonite-finished-chrome-moly-matte-pre-ban

But they caution not to run supersonics with that configuration?

"•Suitable for use with Subsonic loads, either Suppressed or Unsuppressed
•Use of Supersonic loads is NOT recommended with Pistol Gas Port Location"

Maybe that's just them?

 

Are you gonna reload?

[TrickyNicky]

Yeah I'm not sure what CMMG claims that. Also note the gas block seat is .936" so finding a gas block might be difficult. And it might not fit under some free float rails

If you want a pistol length gas on a 16" you have two good options.

1) wait and find a Noveske for $455

2) call Ron Williams

Good point on the gas block, I hadn't noticed that. I haven't decided on what I'm doing with the handguard yet.

  

Are you gonna reload?

Yup, one of these days. :) I'm hoping that having a gun in a round like this will give me the extra incentive to get going. That's what I thought about the 303 though
I think once I finish this build I'm going to start putting my hobby/gun money into reloading. I'd start now but I have everything for another AR except the barrel, gas system and furniture. Its like having an itch having it all just sit there. I'm sure you get it. ;)

[Luke E.]

" If you want the best of both worlds Id get a 16" barrel with a pistol length gas system."


CMMG makes one,
http://www.midwayusa.com/product/657614/cmmg-barrel-ar-15-300-aac-blackout-1-in-7-twist-16-pistol-gas-port-wasp-melonite-finished-chrome-moly-matte-pre-ban

But they caution not to run supersonics with that configuration?

"•Suitable for use with Subsonic loads, either Suppressed or Unsuppressed
•Use of Supersonic loads is NOT recommended with Pistol Gas Port Location"

Maybe that's just them?

 

 CMMG says not to run supers through that barrel because they are assuming that you will be running a non adjustable gas block leaving you with an badly overgassed rifle. I have the barrel and like it pretty well but make sure you buy the smallest adjustable gas block you can find for that diameter gas pad. Syrac seems to be about the smallest i've found but there are likely others out there.

[Luke E.]

 Like Dolomite said, stick with pistol gas and an adjustable block and you will be able to make most any ammo work in the rifle.