Larry - we've had very good luck with RP brass in 8x57. I've tried some Gevelot 9.3x57 brass and the necks were quite thick. I neck new RP 8x57 cases up to .42cal., then size down in a 9.3x57 Hornady die until the case will only just chamber with hard bolt closing. Annealing is not necessary during these steps, nor for one or two firings afterwards. People tend to over anneal. These 'fitted' cases guarantee 0 headspace - the best scenario for starting loading for a rifle. The m46 9.3x57 I have, has a long chamber that is .013" longer than maximum allowable headspace by SAAMI standards - it's .019"(triple the standard SAAMI .006" max allowable) way too long for me. I suggest you do a cerosafe casting or open up the neck of a 8x57 case and do as I've noted just to check chamber dimensions. Because I checked my chamber first, I found the fault, and now it doens't matter at all as my brass fits perfectly. Had I had fired a factory load in my rifle, the primer would almost have backed out all the way. With a heavier almost maximum-type load, the case would have stretched at the web first shot might have separated - and definitley the second would have separated. The M146's and M46's are great rifles, but a few have long chambers & brass must be fit to them properly.

if need be, e-mail me if you want, about this.