Originally Posted by LRSickle
I have three bushings for my Redding die, a .290, .291 and a .293. Right now I'm using the .291. I wonder if I use the .290 bushing if that extra .001 thou would make a difference.
I'd try it on a couple cases to see if it helps. The wall thickness on the .284 case is about .018"!! (Winchester case), and when you add .036" to .264 you get .300. I'd at least shave the necks down to .296. Better yet would be to take the .293 bushing, and size a case. Measure the I.D. (don't use a caliper!). It should be about .263, but I'm betting you'll see something around .258 or less.
If you have access to a set of small hole gauges, then use them with a micrometer. Calipers have flats on the blades, that will give you a little error in your readings. I recommend the set of small hole gauges from Mitutoyo or Brown & Sharp for everyone interested in precision ammo.
Another thing to check on is to see if the cases have the dreaded doughnut at the base of the neck. (.284 cases are famous for this) With the doughnut ring in there the neck wall will expand a little more than the rest of the neck when you seat the bullet (assuming your going deep into the neck)