Hi, So anyone had any success with rifling those caliber? Say I have a way to drill and ream 30mm 4140 bar to the corret size, than I have the access to the correct chamber reamers, all left is the rifling , now,tried the button from ali with little success, used the "high quality" of the Ukraine made with the same results... Im looking into ECM it, and my problem is my very limited capabilities with 3d modeling. Looking to print the mandrel in like 3 segments so ill be able to print it to the length of 20-24 inch it needs to have some kind of groove to align it and glue it all together to 1 piece .

So , just curious, anyone had done this already and willing to share knowledge?