Like others have said the rim lock is due to cosmoline. Mineral spirit was available at Home Depot, so I used it to clean the chamber and all metal parts. I blocked the end of the muzzle with the shooting ear plug, stood the muzzle on soft floor. Then poured Mineral spirit down the barrel until the liquid top off. Left it overnight. Next day, I sprayed water down, and then ran some gun cleaning patches through until they come out clean. Mineral spirit is no longer available, so other light cleaning solvent compatible will work.
The weak mag spring may cause the rounds loading issue.
The weak mag spring may cause the rounds loading issue.

Comment