From what I've heard, the 30-30 in particular with it's wide rim and bottleneck shape lays in the tubular magazine with the bullet nose on the rim of the forward cartridge, below the primer, not against the primer. This would not be true of a cartridge like the 45Colt or 44-40, as the bullet diameter is so much larger in proportion to the rim, they are much less the Christmas tree shape of the 30-30.