This Is how I cut my copper tubing, I'm using soft coiled copper. I made a little jig to make them all the same. I got this chop saw on Amazon it doesnt have a lot of power but it works. I did a lot of trial and error but came up with a 7/8 inch length for the tubing. I was shooting for a 110 gr bullet. I used 3/4 x 3/4 inch aluminum stock for the jig. I drilled a hole all the way through it so the tubing would slide in. Milled a slot for the saw blade at 7/8 inch from the hole I drilled for the tube stop pin. 3/4 inch aluminum works good for the chop saw because the vice on it isn't very big.