Anyone have experience with gas port sizing on 300 bo. I’ve seen several charts with suggested sizes but would like to narrow it down as much as possible. Does anyone have a ballistic advantage 10.3” 300bo barrel, and does it cycle subs reliably without being opened up? I’m seeing that the port measures .081 on this barrel, BUT charts are suggesting .094-.104 to cycle subs reliably.

Thanks for any info.

I had an 8.3" ported out to 0.097 to run subsonic with a suppressor, and supers unsuppressed.

I'm pretty sure both my AR pistols are BA barrels. Both are 10.5", and cycle subs fine. I've used them for some of my 300 blk out ammo testing. The gas port on a pistol may be a little smaller, also. It's generally closer to the chamber area than a carbine gas port, which may be why it's slightly smaller. I'm not an AR guru to know the full in's and out's on exact gas port sizes for each length of barrels, though.

One of my 10.5" AR pistols will easily wear out a 1/3 size IPSC plate at 200 yards when sighted in at 50 yards. They are fun to shoot and VERY accurate in my testing.

Thanks for the info.

I have a little experience but thought I’d see if anyone had the exact same barrel and if it worked for them. I built one using a Nordic components 10.5” 300bo barrel. Their port size was .086 it ran supers perfect but it would not cycle subs. I ended up drilling it out to ~.094 to run subs and that’s how I picked up the sizing range info. Thing is BA says their 300 barrel has a .081 gas port and should cycle subs and supers…just thinking how it’s possible when the Nordic with a .086 port wouldn’t cycle but BA’s with .081 will and wanting verification….I’ll shoot and see I guess and worst case scenario open up the port.