Try giving the gentlemen at Ballistic Products a call.
They have some of the best roll crimpers for paper and plastic hulls around. They can help you if anyone can.
Tell me, are you using a smokeless load or loads for blackpowder? These are normal centerfire cases, and not pinfire ones, correct?
If you are loading them with the holy black or even most of the substitutes, I'd suggest going over to some solid brass hulls, as they will last almost forever if well taken care of, and you can easily top off the shot with a oveshot card sealed in place with Duco cement or sodium silicate (water glass).
Rocky Mountain Cartridge makes new 14 gauge cases, and the quality of their brass is second to none, and heavier than anything else made. I have some of their brass in 10 and 12 gauge and it is magnificent!
Just note that the prices haven't been updated in a couple of years, so they will be
much higher than those posted:
Shot Shell Cases Price List