HalfaDouble,
The smaller head diameter is close enough to make little if any difference, especially if centered in the chamber on the first firing. This is where the larger rim diameter comes in. Where the rim is lager than the rim recess ( some rim recesses are large enough), I reduce the rim to fit, also centering the case( don't forget to put a radius on the inside corner) . Most rims also need thinning, .010-.015". I do this from the rear, which also removes the confusing head stamp, but normally requires deepening the primer pocket with a Lyman primer pocket uniformer. Just load the bullets "out" to the desired overall length. You can use 30-30 the same way, but are really really short. Before boxer primed 9.3x72R cases became available, 38-55 ( original length) cases were often used this way for 6.5x58R S&S, 8x58R S&S, 9x58 1/2 R S&S, 8x57R (360), and 9.3x 57R (360). Then the only other choice was re-drawing 30-06 or 30-40 (or 303 Brit.) cases. Scarce 9.3x72R cases are still fresh enough in my mind ( also I have lathes) that I don't like to shorten any except under unusual cases.
Hoot,
H. UTENDOERFFER/ NURENBERG was the predecessor of RWS. Of course you can PM me, any time you want to.
Mike.
