Mind if I ask some questions and make some suggestions?
Have you shot
any .45 Colt or .454 Casull rounds in the cylinder prior to firing it with .460's? If you have, there will be a ever so slight ring of carbon in those chambers and it will cause signs of overpressure and very hard extraction.
Another thing that I have noticed from/while shooting mine and obtaining groups shot from each particular chamber...(I'm probably the only one that has done this), is that chambers that do not have a round or brass in them will get a good coating of burned powder in them and can become troublesome when you start to use those chambers. This usually happens when you put only one or two rounds in the cylinder at a time and fire them that way. When you choose a chamber that didn't have a round in it when the others went off- it becomes sticky when fired.
.460s must be kept clean in order to function flawlessly. Remember, these revolvers push the envelope of pressure on the design.
Think of it as a fine sportscar...it takes a bit more maintenance than the family mini-van.
If those aren't what's troubling you,
then it's the ammunition.
One other thing...please be careful of pierced primers!!! I had a buddy at the range that used pistol primers instead of rifle ones, and after shooting a box of his hand loaded "hot" rounds, which incidentally pierced the primers, the flame cutting had disintegrated the firing pin and cut the recoil shield around the firing pin hole.
