Do you have a copy of the Winchester reloading guide?
It gives you all the reasons you NEED to crimp the 44 mag.
I have a Rossi Puma in 44 mag,and I use Win 296 exclusively.The guide tells you that you MUST apply a heavy crimp when using this powder.
It would take too long for me to explain here,but if you don't apply a heavy crimp,a roll crimp by the way,you may get 'squib' loads,which is DANGEROUS.
Quite a few reloading manuals have explanations on this.