cmj8591
Member
We don't.
We use the shortened 30-30 case and, instead of necking up to 35 caliber, we neck up to 10mm/.40 caliber. Thus, we have a rimmed, straight-wall cartridge in 10mm/.40 caliber.
I think this overlooks a big reason why they did this the way they did. The round was designed specifically to be used in a lever action rifle. The reason that a tapered case is preferred is to take advantage of the funnel effect getting the round from the elevator into the chamber. Maybe they figure that giving that up to go to 10mm wouldn't be worth any perceived change in hunting performance. A 35 caliber 200 grain bullet vs. a 40 caliber 200 grain bullet in actual field use would be marginal at best. Maybe they just picked that caliber out of a hat.