Measure the barrel length, the length should at least be an even number and not a fraction. It was common to open the chocks by sawing off a short bit from the end of the barrel. Try taking a barrel brush wrapped with fairly coarse steel wool and dipped in oil and then spin it in the end the barrel with a power drill to remove the rust.

Steve

Approach life like you do a yellow light - RUN IT! (Gail T.)