I've found IMR4198 to be a fairly consistent powder, at least on the low-end. I typically use IMR3031 for higher velocity... but with the lighter bullets you are loading, IMR4198 should be more than fine.
For the sake of experiment... and assuming you are single-loading, at least for test purposes... try no crimp, or just bump the case mouth with a taper crimp. I, of course, crimped when I was loading for the 1895, but with my 1885 I have to flare with an M-die (for the cast bullets...) and all I do is tap the mouth back in with a taper crimp die. That would take the crimp inconsistencies out, at least until you can prove your load and move forward.