I have a question on which BCG to use with a 300 blackout.   16in wilson combat match barrel, carbine gas.    Standard carbin buffer and spring.    "I have two Fail Zero BGCs.  A full auto and a Semi auto."        I will be shooting both supersonic and sub sonic.  Subsonic with an ACC SDN6.  

I know the heaver bcg will increase dwell time and delay opening of the bolt.   In a 556 this is good but I do not know which is better in the case of a 300 blackout subsonic.     May Occasionally shoot subsonic without the suppressor.


I did a search for BCG full auto vs semiauto.  did not find what the info I am looking for?


Which BCG would you use and Why?

what kind of gas block are you running?

if it were mine id go with the semi bcg and use an adjustable gas block.

Maybe this BCG will suit you.

http://www.righttobear.com/Spike-s-tactical-lightweight-BCG-p/st5bg05.htm

Fixed gas...   from Wilson combat when I odered the barrel from them, the low profile one they recommended.

I was leaning towards the semi one because of the lower pressure subsonic rounds

I am running a Brownells M16 style BCG.  8.5" Noveske, fixed Noveske gas block.  

220 gr HPBT subs run fine.  125gr SMK  supers run fine too.

wildearp, what barrel length do you have and is it suppressed? I want to build a .300 blk and a suppressor is way out of my budget so I'm not sure I'll be able to shoot subsonic. My barrel will be a 16" with a carbine gas port.


EDIT: Duh, I guess I should read more carefully.

In general I have found that you want to run a semi auto BCG. You don't really need the extra weight.  
That is a general answer.

The specific answer is what size gas port do you have?
What weight buffer are you using?
What buffer spring are you using?
Are you using an adjustable gas block?
Are you suppressing it?
What ammo are you using?

And so forth.

You can tune it later for specific results but I would start with a standard semi auto BCG and a quality C158 bolt.

8.5" Noveske is barrel length and brand.

I have an 8.5" CMMG with a fixed Fortis Low Profile Gas Block and I run an H2 buffer.  I don't think there is any need for me to have a H2 buffer.

Are you building a rifle or a pistol?

Some moto for you



ETA: In response to poster above me, I have only shot 20 subs with a 762SDN6 on my pistol with the H2 buffer. I want to say my port size is .075 but I'll need to verify this. I rarely shoot sub, at least until I have my own can and build a load around it.

My H1 buffer cycles just fine and is probably more ideal for subsonic shooting, as is the semi-auto BCG. the less weight the better. How often do you intend to shoot subsonic?  Supers through a can aren't bad at all and are cheaper commercially.

I just ordered this 8" barrel for $100.  It shipped today so I will be building a new pistol. I am hoping to get it to cycle subs with out a can. I may have to work up a hand load. I don't really want to buy a lot of subsonic ammo at today's prices.

I have been looking at the same barrel and finally ordered it.
Let me know what workup you come up with as I will be loading mine as well.

i tossed an AIM V2 nib in mine.  if i can ever get the thing to shoot more than 2 rounds before falling apart i'll share some thoughts.

MrBear, I'll be building a rifle. The barrel I'm looking at is 16" 1:7 twist with a carbine length gas port with a .106 port diameter. I don't see me getting a can, 1200 bux is just a little out of my budget.  
I would like to shoot subs but if not I'm ok with just supers.

I don't have a oranges to oranges comparison but in my new 300bo using a 10.5" rainier ultramatch (1in8, pistol) I'm using a PSA 'premium full auto' BCG built on the PSA pistol kit  (Father's day sale).   That's with a seekins adjustable gas block but it's opened wide.  I only this last weekend got the specwar for this host  so I haven't had a chance to start adjusting the gas flow down.  I don't know the gas port size off hand of the rainier barrel.

I don't have a problem with cycling subs, 208gr Amax's, in it down to 850FPS without a can although at that low a speed I don't get BHO.  Shooting a 308 at 850fps is a very weird feeling by the way.  Running at 1050FPS I have no issue (11gr of 1680) with feeding or lock back with can on or off.  

It also has shown no problem cycling light supers (TNT, VMax 125gr) without a can although finding a load using 4227 and 300mp for the 150gr sp's I had laying around took more development than I liked since I'm pretty cautious in that regard  to get reliable BHO and feeding.  Not a lot of data for those two powders and I can't find 296/110 to save my life.   300MP is showing quite a bit of promise for supers for what it's worth.   Just no official data except for a very recent nosler update for one bullet weight.

I too have a 16" Wilson barrel on my 300 blk. and have tried both a semi and full auto BCG. Both worked fine but the one that stays in the gun is a full auto one from PSA. Buffer and spring is a standard carbine from PSA. Gas port hasn't been touched and the rifle at around 500 rounds has been 100%. Have not however, shot any subs.

Barrel arrived today. It may be a week or so before I get a chance to build it. As for my over all first impression, the barrel looks good, the machining looks week done. The finish looks good as well. I won't be able to to give you more until I get it put together.