When you install the bolt stop pin keep in mind that it has to get past the recoil spring assembly before it will seat all the way. I sometimes find the need to give it a tap with a rawhide mallet to get it all the way in.
One other thing to check on the 22/45 is the sear spring. The long end of the sear spring can sometime get in the way and bind up the works. Make sure it is against the frame and in front of the hammer pin.