So I'm trying to spec out a reamer for a 20 Grendel (bolt action) and wondering about neck clearances, length and free bore. I picked up a 20 ppc bushing FL die and sized down several Lapua and Starline brass. Lapua ends up at .234" and Starline .232" loaded diameter with a 39 gr Blitzking. I'm building a light carry gun on a Howa mini 7.62 rifle, 11tw Mullerworks barrel. Probably a 23-24" barrel, .560's muzzle diameter. BIB's 40gr are on the menu for this one and I'm told they have a short freebore and to spec the reamer zero freebore. OK, so that's settled, except what neck diameter and do I shorten the OAL on the case since the brass seems to shorten up considerably with sizing down operations. I was thinking of 10-20 thou shorter neck on the reamer and if it's too short I can trim to proper length. Still plenty of neck to seat a bullet and keep the throat back closer to the bullet. I guess it might be relative, but has anyone noted OAL changes when sizing 6 PPC down to 200 PPC? Do you keep the same trim to length of the parent cartridge or will the necked down version end up shorter to some extent? As for neck diameter I was thinking .2375 or just a .238 neck, really don't want to turn necks on these little buggers but maybe its a good idea??. What say you?