Gentleman I have a question. I have a beautiful older Brooks mould. It casts a .410 size 410 gr. (Is that not weird... ) bullet with 30/1 mix. Now....my Sharps #3 in 40-65 has a .408 bore. I really tricked yall.. ...this is a two part question. I have heard both sides of the fence...shoot .001-.002 over bore size...and shoot bore size bullets. Which is best? Secondly...can I size the .410 down to .408 in my Lyman lube/sizer without disturbing the bullet so much that I loose accuracy? Thanks so much for any input. It will be greatly appreciated.
Iron Horse
AKA: Larry Gilley
Life isn't about waiting for the storm to pass...
It's about learning to dance in the rain.
I got good results lube sizing to .410, that's right, just lube, no sizing, I was using a Lyman Snover, cast 20-1, weighing about 422 grns. Also, the gun was a LRE with heavy oct 30" barrel. Shot well, Good Luck, David Barfield
My #1 Shiloh in 40/65 shoots the same size groups (1&1/2" at 100 yds) with .455 bullets at 375 grains and .410 bullets at 425 grains. Try the bullets sized and unsized to see which works better. You will not hurt the rifle.
Kirk's recommendation is to shoot a bullet that is groove diameter size. That is also the recommendation of Steve Brooks, one of the top mould makers and champion master class BPCR shooter. I look at that as being the ideal bullet size. Paul Matthews in his books on casting says he gets excellent accuracy with bullets 1 thousandth or more under groove diameter, with 30-1, as it 'bumps up' to seal. The negative that oversize bullets present, according to Kirk, is potential chambering problems in fouled barrels, and possibly more of a tendency to lead. Sizing 2 thousandths shouldn't be a problem .. the barrel will do it eventually .. so it's probably better to do it in a sizing die for controllable concentricity.
) bullet with 30/1 mix. Now....my Sharps #3 in 40-65 has a .408 bore. I really tricked yall.. 
...this is a two part question. I have heard both sides of the fence...shoot .001-.002 over bore size...and shoot bore size bullets. Which is best? Secondly...can I size the .410 down to .408 in my Lyman lube/sizer without disturbing the bullet so much that I loose accuracy? Thanks so much for any input. It will be greatly appreciated.