If you could secure 200pcs of Lapua 6.5-284 brass that could potentially last the life of the barrel, and I think sizing down to 25 can be done in one step. I think
@willfrye027 has experience with both and will have better feedback on that.
Tough to say with all the variables but based on my experience shooting 133's in a Preferred Barrel Blanks button rifled barrel on a Tikka action, I would say that's a reasonable and conservative expectation. I built mine when they first came out and was just a little bummed that I didn't go with the 284 case for the little extra juice. I just wanted to chime in because Tikka actions usually show pressure a bit earlier than some customs, so if you were looking at data from other reloaders touting faster velocities hot rodding a load, you might not get the same result.