The Thor™ Hammer Sizing Pack is designed for you to size your bore diameter before you place your bullet order. This ensures the truest fit and best accuracy.
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.
**** Before purchasing your first pack of Thor™ Bullets, you will first need to order a test sizing pack of 4 bullets of diameters of .500”, .501”. .502” and .503” that allows you to correctly size your bore. It is important that you start with the smallest diameter Thor™ Bullet, and work your way up in diameter size until you find the proper fitting Thor™ Bullet for your muzzleloader. While manufacturers have similar bore diameters, they will vary .001”-.002" from gun to gun, so it is extremely important to correctly size your bore to determine which diameter works best for you. In the event that the .500 is too tight for your bore, then the .499 bullet will work perfect! Keep in mind that the .499 bullets are only available here on Thorbullets.com via custom order.
To determine which bullet is best for your muzzleloader, start with an empty rifle, remove the breechplug and slide in the .500 bullet. If it slips easily down the bore, you then try the .501 and so on.  When you find the diameter that requires about 20/30 ft./lbs. of force to push down the barrel (that is comparable to the resistance you get loading a standard sabot bullet), you have found the correct size for your rifle.