Thor™ Lightning Bullets are a one-size-fits-all bullet. These bullets are tighter fitting, but no bore specific sizing or sizing packs are needed.
The Thor™ Bullets are high performance, full-bore muzzleloading bullets. The .50 caliber ballistic tip bullets feature a 100% copper construction and are manufactured by Barnes™ using their X Bullet® platform along with their proven expansion technology. The Thor™ Bullet is proven to be extremely accurate at long ranges, while providing lethal expansion on deer and elk-sized game. 
The Thor™ Bullet's hollow base expands when the powder goes off, both gripping the rifling and sealing the bore. These bullets actually shoot 75-100 FPS faster than a Powerbelt, due to their superb sealing power. If it is a quality conical you are looking for, that won’t fragment into a million pieces, the Thor™ Bullet is the way to go. This bullet has a Ballistic Coefficient of .205.