Don't bother with an adjustable gas block on a gun that doesn't fully cycle; you don't need to restrict the gas any further.
Maximum effective gas port size is 1/8" (0.125"), yours won't be any bigger than that.
I'd guess you have a carbine length gas system on that barrel; should have gone with pistol length gas. If you do already have a 1/8" gas port (it's probably smaller than that), there's not much you can do other than making sure the gas block is aligned properly, tube is aligned in the block, and the gas rings are installed correctly on the bolt.
Did you use an H1 or H2 buffer, or extra power spring? If so, ditch those and go back to standard carbine parts.
