I use a small 2" cutoff saw from Harbor freight https://www.harborfreight.com/2-in-m...saw-62136.html I use it for jackets and shell cases. I just make a simple length stop and it cuts a very precise length. The photo's below are rifle brass I cut from basic brass. Very clean cuts.
I have a lathe and mill but for brass I use this little saw. The price has increased since I got mine but it's still a fair price for what it does.