14 November 2007
Sizing in the Lyman 450 is a complex business. I have a DC 314299 mold that casts not-round bullets ~.314". I have sized them to .312", but it ain't .312", it's more like .3124” and shot them for a while new, in the belief that bigger is better. I like to seat bullets as far out as possible without having to whack the bolt handle. The sizing diameter varies the max OAL. For a while now I've been trying smaller bullets, in the hope of finding more accuracy. Sizing bullets a lot = .003” or more in one step bumps the nose up a lot ~.002” sometimes more, if the bullet is soft. Harder bullets are more difficult to get through the 450. Trying to go from .314” to .3095” say gives big noses and bent bullets when soft, and much harder bullets are difficult to get through the sizer.
I can get .314” soft bullets down to .308"(.3085” or so) without damage or hard sizing by .314” to .312", .312” to .3095", .3095” to .308". And I have to run each bullet through the sizer twice turn 90 degrees to get the bands round.
Any sizing at any hardness thru linotype makes 314299 noses bump up, bump dia determined by size jump. If I bump the nose .0015” or more, the max OAL reduces cause the nose now doesn't want to go in.
I've got a man working on a top punch for the 450 to allow downward nose first sizing that should eliminate the bumping.
Its taken a lot of measurement and fiddling to see what's going on with the 450, I'm thinking I'm seeing better accuracy at .3095” than at .312".
I have no mold that casts a bullet round to .0002” and never had one that I know of. All my 30 sizer dies don't hold .0001", generally .0002” or more, hence the 90 degree turn and size again.
The lesson for me has been that sizing bumps the nose, big sizing bends the nose-sometimes, bumping depends on sizing amount and bullet hardness, and smaller bands allow seating out but bumped noses mean max OAL reduces.
I think what all this drivel means is that nose first sizing is probably the way to go.