Thread: Trouble getting 300 Blackout to shoot and cycle subs

I had a similar system but by DSA, shot both flawlessly with a rifle tube/buffer. Problems only occurred once I changed to a carbine buffer tube system.

BTW Lancer mags work great with 300AAC, some of the steel mags don't seem to like the caliber.

Hmmm... threads like this make me nervous. I'm in the process of building my first AR which I'm doing in 300AAC. I'm getting a mega arms 16" barrel and it's a carbine length gas system.... I don't have an adjustable block but I will be running suppressed so hopefully everything goes smoothly... how about using a softer buffer spring for feeding issues?

Originally Posted by clavulanate

Hmmm... threads like this make me nervous. I'm in the process of building my first AR which I'm doing in 300AAC. I'm getting a mega arms 16" barrel and it's a carbine length gas system.... I don't have an adjustable block but I will be running suppressed so hopefully everything goes smoothly... how about using a softer buffer spring for feeding issues?

Nah don't worry, Join the adventure 300AAC is lots of fun!

Changing the buffer weight is probably the easiest. I believe you can open and remove weights (one by one!) on most buffers. 130gram H2 buffers seem to be recommended.

I'm running a 16" carbine gas with a carbine buffer system, I have gone to a semi auto BCG to get bolt weight down, and I have changed powder from 2205 to 2219 with 220SMK, they will now reliably cycle subs but no bolt hold, I would love to try AA1680 powder but you can't get it in NZ. BTW, it is suppressed and I am also running an adjustable gas block but have it wide open for subs. Ideally you need a barrel with a pistol length tube. If I had to build another I would sacrifice a little speed with supers and go a shorter barrel with pistol gas.

Originally Posted by Mathias

Have a look at this link. Just breezed through it but it could be of help before you get the Black & Decker out.
300 BLK Port Size Testing

hey thanks! great link and some interesting reading...... my conclusion for my set up is that according to that my port should be big enough @ 0.112 suppressed, but I'm thinking of drilling out to 0.125 anyway (as 300_BLK has advised) and run an adjustable gas block if I need to reduce gas for the super loads.

Originally Posted by 300_BLK

No such thing as over gassing with direct impingement as the carrier moves away from the tube venting the gas anyway.

You should have an adjustable gas block and pistol length or shorter gas system to reliably run both subs and supers.

Short of changing your gas system I would recommend increasing the gas port to the internal diameter of the tube. You can't get any more gas through than the diameter of that tube anyway.

Remember when testing subs to start high then work your way down. When you have your desired load fire a single round in the mag to see if the bolt locks back, this will indicate if you have sufficient gas to work the action.

Other fixes include removing one coil at a time from the buffer spring until this works and changing to a lighter buffer. Google h and h2 buffer weights to speed up or slow your bolt.

Good luck.

Hi thanks! I'm thinking of increasing the gas port, do you have any suggestions on loads?

Originally Posted by Dr. Watson

Get an adjustable gas block, it's not just a matter of under or over gassed.

Iv had lots of really strange things happen with the gas systems on ARs.

Also it's hard to trouble shoot without first being able to control the gas.

+1

The Doc knows what hes on about...

Originally Posted by Burgs12

Hi thanks! I'm thinking of increasing the gas port, do you have any suggestions on loads?

PM'd you

good reading and videos . .. sure makes a bolt gun in the BLK look an easier proposition

How did get on is the problem solved?