Crimping, if absolutely necessary, in general is destructive to accuracy. That said, I've used it in hand gun loads, to remove the belling necessary to seat a bullet without shaving lead. I use only the amount necessary to remove the bell, and to prevent bullet movement in recoil, no more, and I have 40 yrs of loading notes to prove to my satisfaction that less is better.
In rifle loads, and only with lead alloy bullets, I use it again, to remove the belling necessary as part of the bullet seating operation. I have found that even .44 Magnum rounds, shot from a Marlin 336, require minimal crimping to prevent movement in the tube magazine.
In all of the testing I've done, both bottle neck rifle loads as well as straight wall rifle (.38-55) and pistol loads, a taper crimp gives me better accuracy; and too, I would add, that unless you keep your brass trimmed to the exact same length, a taper crimp will always result in a more uniform neck release force....Bart's comments are right on the mark in that regard.
If your .444 needs the crimp, then use the minimum necessary to prevent the above...in my experience, the amount necessary is barely visible to the naked eye. Remember that lead alloy bullets are deformed by crimping, to a greater or lesser extent. The softer the alloy, the greater the deformation. To prove this yourself, seat a lead alloy bullet, then use an impact bullet puller to remove it, measure before and after and see the difference.
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