brngiese, Thumb safeties are not drop in parts. I have fitted a number of them and I have Very Rarely ever had one that would both drop in and function properly and safely. If a new safety drops in, and can be moved without resistance between the safe and fire position, chances are it will not block all sear movement in the safe position as it should. Apparently, some 1911 owners think that if they can get the safety in the gun, and it will move up and down, they're good to go. WRONG. On several occasions I have seen folks posting about how their new thumb safeties just dropped in, or that there's nothing to "fitting" one, is Colt's caution about a "scant safety" situation really a big deal?,etc,etc. I'll just say that in the three Colt O-frame armorers schools I've attended, the classes sure went through a lot of new, unfitted, thumb safeties to learn to fit them correctly...ymmv
ps, Yes there is "fitting and filing" required. A new hammer pin that does not protrude from the right side of the reciever, i.e., is flat on the right end, is normally needed just to clear the right side of the ambi safety. The right side lever may be secured in different fashions, depending on which ambi safety you use...
Last edited by rock185; 06-22-2013 at 08:09 AM.