Just as info for hand loaders beginning to utilize a mandrel. Recently blew out some Lapua brass in my 40X 260AI and decided to apply a .262 mandrel for the first time in load development with my next loads. My loaded round measures .294 and I was intending to use a .292 bushing. But, in order to realize any "help" or inside touch by the mandrel I had to move down to .291 bushing. My neck thickness measured with a micrometer .015 with very little variances. .0005 to .0007 either way.
