Answer:
I havenever heard of a .54 cal but no, a bullet that will not stay in place for the striking pin will not fire, DO NOT TRY IT, if by some off chance that the striking pin hits the firing cap then the bullet has already started its trajectory at an angle and will probably damage the gun and yourself, it will be hard to find but you may be able to find a a saboe for that caliber, but you may just want to go buy some .54 cal ammo...