Sizing for 38 spec. vs. .357 Mag , which die ???

[10 Spot Terminator]

Just picked up a used 450 Lyman lubesizer and am getting ready to size various boolits I have cast for my .38 spec. model k14 and .357 mag. model 66 Smiths. I cast the boolits I plan to use for the .357 out of wheel weights as will be pushing them harder than those I cast out of 20 to 1 alloy for the .38 more for target and plinking . My question is this ,,, with the harder alloy for the .357 is it better to size them at a true .357 diameter and for the softer .38 special size to .358 so as to promote better obturation under lighter loads ???

[Echo]

Depending - depends on the diameter of your chamber throats. Size your boolits to a skosh larger than the throat diameter (skosh being maybe .0005). I like to size my pistol boolits fat, basically as fat as will nicely chamber.

[Bret4207]

10 spot, obturation is neither needed or desired with a properly fitted boolit. Measure a case mouth ID from a case fired in that gun with a full powered load. I'm betting that will be some where in the .359 area and that's about where I'd size. There will be the odd gun, but most Smith 38's and 357's I own like at least .358 and .359 works better.

[MtGun44]

Try throat diam (FRONT of cyl) or throat +.001 or +.002. See what shoots best.
For me, .358 is great for several diff .357s and M14/15s.

Bill