Contender barrel dovetails and locks are all the same size from the factory. By default these dovetail mounts need to be tight, so you don't want them to be a simple "slip-fit". With a barrel well supported and protected in a vise, I never had one that wouldn't start with a sharp smack or two to a brass punch.
If the lock has been missing from the barrel for some time, it's possible the dovetail in the barrel is tighter than normal due to being slightly peined over, burred, etc. Also maybe check to see if the dovetail in the barrel has been staked, a fairly common practice when a lock shoots loose or has been removed and reinstalled too many times.
Just some thoughts... HTH.
L.
