The size of the bullet
The key factor of an accurate load it the appropriate sized bullet. In the elder days, there was the rule of thumb: .451 ball for the .44 Colt, .454 ball for the .44 Remington and .375 Rb for .36 revolvers. This list can be used merely as a guideline: it is not the type of firearm used that counts, but the diameter of the rifling and the chambers – besides the powder charge, of course. If you are curious about the needed size, just grease a .457 cal. ball and push it through the barrel with the help of a wooden rod. Measure the rifling cuts and use the exact same diameter, or +0,001″ ball. Compared to the diameter of chambers, the projectile is oversized, so when it is pressed in, a thin lead ring is cut off.
You do not experience this when shooting original revolvers. Those chamber’s wall were not paralel, but slightly cone-shaped. Thus, the loaded projectile just stuck as it pressed in. Replica revolvers do not share this feature. The projectiles are oversized and the inner diameter of the chamers are constant. The edge of the chamer cuts a ring from the ball when pressed in, so the bullet seals the chamber from sparks of a shot fired, and combinated with quality grease, it prevents chain ignition. (Chain ignition can also start from the other side, when a cap fall off the nipple, the sparks can ignite another chamber. It is imperative to have your caps seated well on the nipples.)
So, the chamber determines the diameter of the bullet. In a perfect scenario, it’s measures the same as the diameter of the grooves of the rifling. But a slight difference does not mean that your load won’t be accurate. When the projectile hits the forcing cone, it becomes a little pressed and it fills the rifling perfectly. But when the difference is more than 0,005-0,006″ it is better to have your chambers reamed. (Ask for the service of the qualified gunsmith!)
The ideal measure of the bullet also depends on the powder charge. When the chamber cuts the ball, it also alternates it’s shape, the ball becomes a little ogival: a cylindrical surface is formed, which touches the inner side of the chamber. The bigger the diameter of the original bullet, the greater this surface will be. How can we benefit of this? The answer is simple: the lower the twist rate of the rifling, the bigger the needed charge. The bigger the charge is, the velocity of the projectile will be also higher. Thus, it needs more contact with the rifling in order to be twisted right. According to my experinces: if our Remington needs a .451 ball because of the rifling diameters, but the twist rate is slower than 1:19, it is better to use .454 ball.
Keeo in mind: only pure lead can be used to cast balls for your muzzleloading revolver. Do not add tin (or any other material), because it will be a pain in the ass to press the projectiles into the chamber. Some can even damage the loading arm… it happened!
If you want to develop an accurate load for competitions, use a round ball. But if you want to play some steel challange or cowboy action on smaller distances, it is better to use a conical bullet. These are heavier projectiles and will flatten your target easily – however, the loading is slightly more difficult.
The powder charge
Every muzzleloader revolver has it’s own limits because of the limited space in the chamers, behind the bullet. So, the maximum amount of load will be that volume, when the bullet can be just pushed in correctly. During proof testing this is the test charge and no revolver which can not handle this will be let to hit the markets.
But no revolver will be accurate with the full-capacity charge. Basicly, the twist rate is the key factor and determines which charge will be awarded with a tight group size. If the rate is high (above 1:19″) then the charge will be relatively smaller, and if it is slow, then it will favor the bigger charges.
These revolvers work great with 3Fg granulation size powders and you can choose a cheaper brand, if you use quality grease on the chambers.