From what I've picked up at a lever-gun forum, the overall length of the ammo is important to getting the lifter to put it through the guides. The profile of the projectile is important to getting the ammo into the chamber.

I've only used 158gr jacketed and soft-point ammo in .38 and .357 in my 1892 style lever rifle, so I can't comment about your specifics.

Good luck.