Got my first ml coyote last fall while deer hunting. Was a .50 cal round ball at 145 yards.
Balls make nice round holes going in and coming out. Very little hide damage.
A .45 RB gun would be a great choice for coyotes.
The balls take more time to learn to shoot and need to be loaded in the right kind of barrel, but they are cheap to shoot and there's nothing like getting a lot of practice with any gun.
The .50 I used last year was a traditions deer hunter with a 1/48 twist that I bought for less than $150.
