Mickey Duck. never fired a round through the gun, we run a 303 case through the 250-303 lee dies and the case would not chamber. I believe we then used a 257 Roberts sizer die to bump the should back until the case would chamber in the gun. we trimmed the neck to the same length as the original specs.we then loaded 2 rounds with light loads and fire formed them to get the actual chamber dimensions . We then removed 50 thou from the bottom of the die, rounds will now chamber just need load information for shorten case
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