If they are upper end .44 Mag loads, you need to use all the roll crimp you can without damaging the bullet or crumpling the case. The roll crimp should be all the way to the bottom of the crimp groove on the cast bullet, or to the bottom of the cannelure on jacketed bullets. It's near impossible to give an accurate measurement of a firm roll crimp, but the above is what you need.
Magnum powders like 2400, WW296, and H110 need a firm crimp to get a clean burn started.
It also will prevent bullets pulling from recoil.
If you are loading mild target loads with fast powder, very little crimp is necessary.
Just slide your thumbnail over the case mouth and if you can't feel the edge, that is enough.
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