I've never owned the RCBS tool, specifically, but normally these cutters just cut a flat bottom. Remember, though, the feet of the primer anvil only touch down around the outside of the hole, so that depth is all that really matters.
There is no exact stop for seating a primer. The feet of the anvil touch first, so you feel increased resistance there. But you can continue to squeeze it deeper as the anvil squashes some of the priming mix between its tip and the inside bottom of the primer cup. The mix between the cup and anvil is called the "bridge" of priming mix between them. Seating the primer to control that bridge thickness is called "setting the bridge" or "reconsolidating" the primer, as I described two of my posts back.
The late Creighton Auddette first brought this up in the last articles he wrote for Precision Shooting before he died. 1994, IIRC. He said he'd found primer ignition effectiveness was influenced by the amount of reconsolidation. That is, the didn't simply fire or not fire, but rather the energy and speed of ignition was influenced by how much of that pre-loaded squeeze pressure there was before the firing pin hit it. Hackett's observation suggests, though, that once you get the primer seated far enough, additional benefit is small.
I can't tell you if 0.004" deep is deep enough for good function by the old Olin criteria unless I know the depth of the primer pocket and the height of the primer before you seated it. If it was a uniformed primer pocket -0.132" deep, then the primer cup being -0.004" deep would be about right for primers that were 0.130-0.134" tall before seating and having its bridge set. For other primer heights, take the height of the primer before seating, subtract 0.004" (for any primer except Federal, for which you subtract 0.003" for large rifle), subtract the result from the primer pocket depth, and that will be your target depth below flush with the outside of the case head.
There is no exact stop for seating a primer. The feet of the anvil touch first, so you feel increased resistance there. But you can continue to squeeze it deeper as the anvil squashes some of the priming mix between its tip and the inside bottom of the primer cup. The mix between the cup and anvil is called the "bridge" of priming mix between them. Seating the primer to control that bridge thickness is called "setting the bridge" or "reconsolidating" the primer, as I described two of my posts back.
The late Creighton Auddette first brought this up in the last articles he wrote for Precision Shooting before he died. 1994, IIRC. He said he'd found primer ignition effectiveness was influenced by the amount of reconsolidation. That is, the didn't simply fire or not fire, but rather the energy and speed of ignition was influenced by how much of that pre-loaded squeeze pressure there was before the firing pin hit it. Hackett's observation suggests, though, that once you get the primer seated far enough, additional benefit is small.
I can't tell you if 0.004" deep is deep enough for good function by the old Olin criteria unless I know the depth of the primer pocket and the height of the primer before you seated it. If it was a uniformed primer pocket -0.132" deep, then the primer cup being -0.004" deep would be about right for primers that were 0.130-0.134" tall before seating and having its bridge set. For other primer heights, take the height of the primer before seating, subtract 0.004" (for any primer except Federal, for which you subtract 0.003" for large rifle), subtract the result from the primer pocket depth, and that will be your target depth below flush with the outside of the case head.