I checked the dimensions on the expander and determine it is 0.435 so it may be oversized

The challenge is not the pocket is over expanded. I can set the depth to not do that or simple skip that stage. The problem is when I put the cartridge through what I believe is the final die that sets bullet height and crimps them solid it does not crimp them tightly. I can still move the 0.423 bullet in and out with light finger pressure. I did a few 0.424 bullts which worked better, but still not tight.

I measured the fired brass internal case mouth dimensions and they ran from 0.428 to 0.431. I continue to wonder what the hell on bullet bore dimensions. This might lead me to think I need a bigger than 0.423/0.424. I went back and remeasured the muzzzle and the casting of the chamber, and barrel slug.

The gun is stamped 10.75x52R B.BLINDEE and the bores should be about 0.423 to 0.424, or so I think. The rifling while not deep appears to be in good condition and I do not think it has been bored out.

I remeasured the muzzle is 0.429 or so groove to groove. the bore slug 0.427 (which I did not get all the way through the gun). I am beginning to question my measuring tools and there ability to consistently read. That or my technique bites, and or all of the above. Part of my challenge is meauring the lands versus the grooves (Yes I realize this sounds stupid) I was measurung groove to groove versus rolling the casting in the caliper to get the land to land.

In checking what bullets will slide into the fired brass the 0.427 seem to just barely slide in the .430 stuff does not. I have discovered that even unresized bullets in the same box can vary 0.002+-.

I am nervous about increasing the bore dimensions of the bullets I am loading as it could effect pressure significantly. At the same time accuracy with the 0.423 bullets is good as was the 0.424 ones I fired.

I believe I will go back and reslug the barrel with a 0.427 and a 0.424 slug (I would do 0.425 except that die is still not here yet.