Tt ar50 primary trigger on older armalite ar50a1 - Triggertech Armalite AR-50 Primary Trigger

I did not read the fine print to realize this trigger is meant for the newer versison, the AR50A1B. After searching around for a replacement I didn't want to go thru the hassle of returning it and having the same issue. I noticed in online pictures that the receiver on the new AR50s are milled down a bit in the trigger pin area. After test fitting and investigating, I simply filed down that area about .090" and the triggertech dropped right in. Much better than the antiquated adjustable Shilen that it came with. Breaks like glass and I set it to 1.5lb.