I would drill and tap the bottom of the sight housing (After it is off the barrel) and put in a small (6/32) set screw. Then, put the sight back on, shoot to index properly, mark that spot. Remove the sight housing, put green locktite on both the barrel and inside the sight housing, out it back on the barrel, index it and lock it down with the set screw. The screw is not there to hold the sight on, just to keep it in place so the locktite will set. If you insist on the pins, drill after the locktite is set up and put the pins back in.
This is the method I use on match AR barrels and it works very well. I never use the pins on AR's however.