R.E.A.L bullets are tapered so it will fit into barrels with a variety of bore/groove dimensions. Unlike SAAMI standardized cartridges, there is no agreed upon standard for muzzleloading rifle or pistol calibers. The largest diameter is .467" at the top of the bullet and graduates down to .005" increments on each band, ending at .452"
By stepping the driving band diameter of the REAL bullet up from the base, one of the grooves is going to be large enough to engrave into the rifling. On the looses barrel the bullet will drop in all the way to top driving band, in the tightest barrel you might have to push the bullet in with your thumb to engrave the base band.
