Personally I like 2400 powder in the 44 magnum. Along with a 240 grain cast bullet. You can start at 18.0 grains of powder and work up. My best loads are normally around 20.0 grains of powder. You can also work this powder down slowly for a great low recoil practicing load. I like 2400 because you can get enough powder in the case so that you will not have any case position problems with your load.
Now when it comes to crimping in a single shot. You do not have to do it as long as you can get your neck tension right. However I would suggest that it is better to crimp your load. I know for a fact that my SD's are cut in 1/2 when I crimp the 44 magnum and 45 Colt cartridges.
The crimp gives a more consistent combustion. And also give a better powder burn, and the barrel will not get nearly as dirty with a crimp. If you do not want to crimp then I would probably go with a faster burning powder. But then that opens up other problems. So my advice is to apply a good heavy crimp, and trim all cases to exact length. Tom.
I load for a half dozen different 44 mag's. Both single shot, lever action, and revolvers. I put a heavy crimp on all the loads for all of them. I cast my own 240 grain bullet from straight WW with no GC. Tom.