If you take a set of badgers and remove the screws, then drop the ring cap onto the lower, the opening for the upper is wider than the opening of the lower. Like S1 has said, the gap between the rings is needed to ensure you're putting the same amount of pressure on the tube and the area holding the tube is round and not oblong.
If you ream the lower out to match the upper, I don't see how you could put enough torque on the cap to hold the scope. The cap would touch the lower half before it put enought pressure on the tube.
I may be looking at it wrong,, but I will keep the gap in all my rings.
Also, after I lap a set of rings I blue the clamping surfaces, and lightly oil them. I've haven't had a set rust yet, nor have I had a scope slip, and we shoot in everything except lightening. (save for that last one JOHN cancelled becuase it was 10F [img]images/icons/grin.gif[/img])
All the times I never lapped rings I never had a problem. I like the Burris rings because I know there won't be no matter what angle they're at. No marring or scratching the tube either. I would be interested to know if anyone has had good luck with them using the NF scopes or an equivilent weight scope?
I made my own bases for a set of Burrris pos-align rings. I just milled the dovetail off the bottom of the front ring and put in 2 8-32 screws up from the bottom in the base. The ring sits in a very shallow v-groove that is lateral accross the base. The fit is tight for the ring. The rear ring uses the windage screws and also sits in a shallow slot. As much as I like my Burris stuff, I can't say I like the base's with the twist in gizmos. They just stink. Mine was destroyed the first time I put them together. After that, I just made my own arrangement. I will say the top halves are hard to beat. If you use the optional offset ring kit, you can get 40 minutes of elevation out of em. That's more than a Signature 8-32x44 has elevation. If S1 is saying they make a set that goes on dovetails, get them and be done with it.
As for saving the finish, I have a 30mm 8-32 BD on my match gun and it's been off at least 20 times in the last year. It doesn't have a mark on it.
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
Your observations of rust on the rings is why I do not like lapping or reaming rings. If rings are already sized to fit the scope, any material removed only makes this "hole" bigger. This leads to less contact with the scope tube and movement.
If someone made undersize rings, then lapping would make a lot of sense. You would get an exact fit. Bedding scopes does not usually work as epoxy will move with repeated vibration and your scope will turn in the rings. Epoxy is also "soft".
Check to make sure that the bases are well aligned and adjust if necessary. If the bases are straight, so will the rings from a reputable manf. Certainly enough to not damage your scope and hold things firmly.
Personally, I love the Burris sig rings and use them whenever I have to shim a scope for more elevation. They are very strong and the inserts hold rock solid. They eliminate any alignment issues between rings and bases.
If lapping or reaming is what you choose, never let the two halves touch. This guarantees that you have no idea how much force is put on the scope to hold in place. The rings are now useless unless material can be removed so that there is a gap between the halves again.