The style of a rifling really has nothing to do with whether they will work with paper patches or grease grooves, both bullet types will shoot equally well in any kind of rifling.
The big bugaboo with your rifle is that I believe it has extreme taper to the bore. I had a Martini 577/450 With the same remarkable taper, and it was extremely challenging. Because I shoot paper patches almost exclusively, I did not have a .458 bullet to work with. I found patching up to meet the diameter of the lands in the throat required so much paper, that I never really did get anything like decent accuracy. I believe my land diameter at the top of the throat was approximately .472 as I recall.
In any event, I would suggest getting a decent custom mould from Buffalo Arms with a diameter to match your paper in making bullets the land diameter of your barrel at the top of the throat. Paper which is not more than 2x the height of your rifling is best. Always start with the paper when specing out a custom mould. BA moulds are pretty much the benchmark in lead bullet molds. They are worth every penny.
I would be interested to know how they made such tapered bores In their rifles. The depth of the rifling does not change throughout the length of the barrel. They must have used some pretty interesting techniques to do that.
Good luck with your rifle.
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
