What sizing die should I use for 45 ACP?

kolar55 wrote: Hi all. This probably has been discussed before. I did a search and really couldn't find the answer I was looking for. I poured a chamber cast and muzzle cast with Cerrosafe in my Gold cup .45ACP and both measure about .4505. I will be shootng the 452460 SWC. Should I get a .451 sizer or .452? Thanks Lonnie

Correct sizing diameter for an M1911 pistol is 0.0005” under chamber throat size.

Chamber body diameters of military pistols are large enough to accept .454 or .455 diameter bullets without having to use the Lee Factory Crimp die to profile the case body after bullet seating. In new after-market match barrels with short throats accompanied by an abrupt origin of rifling, seating depth and overall cartridge length must be carefully adjusted to prevent the ogive of the bullet from impinging against the angle of the forcing cone.  In match guns it is common to control headspace of loaded rounds by regulating exposure of the front driving band so that it just barely makes contact with the origin of rifling.  This must be done carefully without causing any resistance to chambering or extraction.  Getting reliable function requires brushing the chamber as needed and 100% check of rounds in a drop gage.  

The easiest solution is not to worry about as-cast bullet diameter. Instead adjust bullet seating and crimping so that rounds fall completely into the chamber of the barrel removed from the gun, of their own weight.  Visually confirm correct headspace by holding a steel scale across the case head to observe that the cartridge head neither protrudes above, nor falls below the face of the barrel hood.  Some people do a simple fingertip check.

After-market match barrels of minimum dimensions are more prone to functioning problems caused by variations in case body wall thickness and mismatch of bullet diameter.  Use a Lee Factory Crimp die to full length loaded rounds so that they enter the chamber fully without resistance.  On test dummies mark the exposed front driving band or ogive of the bullet. Adjust seating depth and cartridge OAL by trial and error by hand functioning inert DUMMY rounds to be sure that rounds feed, chamber and extract freely with only minimal visual marking of the bullet. 

If loading ammunition for several guns, tailor the ammo for the tightest chamber with the newest barrel and moderately soft alloy such as wheelweights will work fine with any bullet which fits from 200-230 grains using normal wadcutter changes in the range of 4.5 grs. of Bullseye or 700-X, or 5 grs. of W231.