Going through the throats is the first test. How do the bullets go through the barrel? If the bullet jams up when it gets deep in the forcing cone, that is good. Then you take a soft lead slug and drive it through the length of the barrel (you can use a soft lead bullet, but it is likely to be a little harder to drive it through) and measure the slug (this is called "slugging the bore").
The measurement of the slug tells you the size of the bore (if the pressure to drive the slug down the length of the barrel was even, that is good, if uneven, you have a different problem). The size of the bore should never be larger than the cylinder throats. However, in your case, the size of your bullets.
Here's the theory: Bullet leaves the case. Sometimes the pressure behind the bullet will "upset" the bullet (make it fatter), especially if you are shooting a hollow base bullet. This helps the bullet fill the barrel bore and engage the rifling. Filling the bore keeps hot gasses from getting up alongside the bullet and melting it, thus leading your bore. Engaging the rifling helps accuracy.
After the bullet leaves the case, upset or not, it goes through the throat, which swages the bullet to the size of the throat. Undersized throats in revolvers is a major problem with leading and inaccuracy. Since your throats are clearly over .454" this is unlikely to be a problem with your revolver (unless you find your bore to be larger, which is unlikely).
Leaving the throat, the bullet then passes into the forcing cone, which again swages the bullet to perfectly match your bore dimensions.
If you bullet seals the bore, you get little leading and the most consistent (and highest) velocity with that ammunition.
Happy shooting.
Lost Sheep
