A Contender has multiple safeties, the frame itself has two, internal safety is activated by the barrel locking lug, pushing a internal turnstile like flat piece that prevents the spring loaded hammer block from dropping. If the barrel locking lug will not slide back into its frame notch far enough for the hammer block to drop, the hammer will not catch nor will the gun fire.
The hammer spring should hold the block in place, until the hammer is pulled back, then the spring loaded hammer block, should drop with a clack.
The proper method to adjust the barrel locking lugs is to remove the lug(s) from the barrel, the lug is held in with a pin, and then with with a high grit wet and dry paper, on a flat surface, I use a plate of glass, with oil, polish the flat bottom of the locking lug, do not polish the top, leave the factory angle alone.
You can easily take off a couple of thousandths or so evenly from the flat on the bottom of the lug, not so, from the angle on the top.
As with all guns, steel fitting, requires patience, you can not readily replace too much cutting. Some of these Contender parts are getting hard to come by.
