A bit of a thought on the common diameter for a few cast boolit cartridges... To use this, just find your caliber and take the Bore size as the "size-to" diameter for the bore riding portion of the boolit.
Please note that for period weapons, this could be way off. Fer instance, look at the bore diameters of the 256 Newton... To find out what SAAMI thinks that your cartridge should be, go to http://www.saami.org/specifications_...tion/index.cfm and look for your cartridge.
Cartridge Bore / Groove
223 Rem (22) .219 / .224
6mm Rem (24) .237 / .243
257 Robt (25) .250 / .257
264 Mag (26) .256 / .264
6.8 SPC (27) .270 / .277
7-30 W (28) .277 / .284 (take note, owners of RCBS 145 & 165 SIL boolits!)
30-30 (30) .300 / .308
7.62x39 (30) .300 / .310
32-20 (30) .305 / .311
303 British (31) .303 / .314
32-40 (32) .315 / .320
8x57 (J) (32) .311 / .323 (S bore is uncommon. Smaller!)
35 Rem (35) .349 / .357
357 Mag (35) .346 / .355
375 Win (37) .366 / .376
45-70 (45) .450 / .456