Would like to build 9mm upper from Henry on this board, I want my barrel to be threaded, he give out two option '1/2x28 or 1/2x36'.  I have no clues as to which one to go for in terms of pro or con? thanks.

Quoted: Would like to build 9mm upper from Henry on this board, I want my barrel to be threaded, he give out two option '1/2x28 or 1/2x36'.  I have no clues as to which one to go for in terms of pro or con? thanks.

Buy from Henry @ Title2 with confidence.   As to the thread issue, go 1/2-28, as if you decide to buy a suppressor, 1/2-28 is the common thread... If you choose to use a std flash hider, be aware that you will need to bore the existing 223 hider to pass a .355" slug, not a big deal, hit it with a 3/8 bit and carry on.  Just do not grab anothe r 223 hider and install by mistake.

There is not much option for 9mm hiders, (1/2-36, and command a premium $$)... 223/556 is more common, less expensive, just make sure it will pass a .355" bullet.