have the proper thread tap of the buffer tube and OSI jig, you would have to cut the hole to the perfect dimensions, I could cut the threads
my tap is not a cheap one
the only problem I have is you are using steel, I have only used aluminum 0% DSA and 80% Tannery blanks.
so is it a thin peice of steel I can clamp to my jig and tap the threads if so its possible for me to do. I am out of town right now and on the road so if time is not essential
send me a PM to discuss further