What size should my bullet be?

I have a new Miroku/Winchester M1892 357 Mag/38 Spl.
A pounded cast of the Chamber/Throat gives a ball seat diameter of .379". Groove diameter of .356".
Pin gages ( Minus .0002" gages) in the muzzle= .346" go, .347" no go.

I am about to order a mold. What size bullets should it throw?

Rocky I would order .357 if it's .356. Some would say .358 but I error on the side of caution with your pin guage.

I may have misidentified the "ball seat diameter" There is a section .058" long and .379" in diameter from the case neck to the tapered section, which is .096" long, tapering to the groove diameter of .356". There may be no "ball seat". This may be an extension of neck diameter.

rockydoc

Shoot the largest bullet which chambers without resistance. Read last section of the sticky.