Bore Ridding bullet bore dimensions

[ohland]

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_and_information/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

[MT Chambers]

Good info., I usually stick the bullet a ways into the muzzle and see how that fit is.

[ohland]

Good info., I usually stick the bullet a ways into the muzzle and see how that fit is.

Well, these standardized dimensions are just that. Look at the notional SAAMI spec drawings and your physical bore may have a +.001 or so tolerance.... Another fact of life is that the breech end and muzzle bore diameters may be different... So you are ahead of the game by sticking one in the muzzle.

For myself, I tried sticking a RCBS 7mm-145-SIL into a .278 H&I die with my fingers and after some effort, it went up to the first drive band. When my .277 H&I arrives, I'll clean up the noses on my 20 or so 145s and try loading them up in my 7-30 Waters.