FWIW,

I was reading an article that was written at the time the 52 was introduced and they did exhaustive testing of handloads. They got the best accuracy with a slight taper crimp. Based on this I put a Redding taper crimp die in the last station of my 650. The accuracy is very good, but I don't know if it's better than the slight roll crimp I used previously. I think the key is to not use too much of whatever crimp you use.

Jeff