Yep, we tap and thread all our lowers when we make them, and put in a 4-40 x 1/8" long set screw to hold the spring in. Any tap will work. It's soft aluminum, but always take your time and do it a little at a time (start the tap, back it out, tap it further by one turn at most, back it out.... repeat until you have around 1/4" of good thread.)