Lutnit, .430 is a little small for most 44 magnum rifles, .432 to .434 usually works better. Saami throat specs are different for rifles than pistols. Marlins usually like .432 dia.
Oh, I know all about that
I appreciate the advice though. I didn't find out about that until after I had to clean a lot of lead out of the bore several times (and still had to clean a lot of lead out after that as well during my experiments).
I've been struggling with this rifle for a couple years trying to get cast bullets to work. The barrel slugs .4315" but for whatever reason the .4305" PC'ed bullets seem to work and are accurate so I wont complain. I've tried .429", .430", .431", .433", .435", and .438" (round balls) in soft cast, hard cast, gas checked, plain base, small wads in the cases under the bullet, low velocity, high velocity, and all other normal "solutions" to getting cast to work in a Marlin Micro Groove barrel and none of it has ever worked. I either get tumbling bullets or horrendous leading in the bore. PC'ing was my last-ditch attempt before just giving up and relegating the rifle to jacketed bullets only but it seems to have worked (at least with H110, don't know if these IMR4227 loads work yet).
My .430" 240gr SWC mold would drop as-cast at .431-.432" or so and I would PC them up to .432-.433"-ish, not size them, and they seemed to work at higher velocities as well. Meant to do some more testing when I realized the mold is damaged and all the bullets come out with fins on the bases. Been meaning to order a replacement since it's a design/weight I'd like to keep around for any potential 44 revolvers in my future.