I have a vintage Marlin Model '94 in .44-40 built in 1905. It slugs to .426" and will chamber factory Dominion ammunition ( miked at the neck with a jacketed bullet at .441") without difficulty. I want to handload 200 grain R.C.B.S. flat nose flat base cast bullets sized to .429" but loaded in Dominion cases, and even most Winchester cases, the outside neck micrometer dimension is .446" and these shells will not chamber in my rifle. Even cases holding bullets sized to .427" will not chamber. What is the collective wisdom as to how I can overcome these difficulties ? I really don't want to be loading jacketed bullets, and the only solution I can come up with is to open up the throat a little to .448". This may be the wrong part of this forum for this question ? If it is please advise me.