Haven't had a lot of time to do some extensive testing, but here's a video I got of it last week.
This is the 6.5 PRC upper, it works a bit better, but is still over gassed. I tried both the Griffin Armament +15% extra power spring, and standard AR 308 carbine spring, both seem to operate the same when firing. I've got the Superlative Arms bleed off adjustable gas block installed on it now, so I'll see if this helps the over gassed issue by bleeding the excise gas out. I'm also going to try this on my 300 WSM barrel as well. I haven't ordered another test barrel yet, but I can get one with a .064 sized gas port. I'll start testing with that and drill the hole bigger if I need too.
I've decided to try all of this before going with a rifle length buffer tube and much heavier buffer, I'd like to see how my theory works with the bleed of gas block and smaller gas port.