This is from Handloader Oct.1992. Elard Mock recommended after testing, a protective mild steel seamless tube that slips down over the brass primer magazine tube as
far as the knurled ferrule. It's dimensions are 7/16-inch O.D. x .049-inch wall x11-3/4 inches in length. Also a,stainless steel protective collar encloses the primer magazine socket with dimensions of 1/2-inch O.D. x.028-inch wall x1-1/16 inches in length. the collar cannot extend higher, otherwise it would interfere with the tool head at its lowest operating position. Also, the collar may not clear the knurled ferrule in some cases of tolerance built-up. If so file down the knurled ferrule to fit.
Hope this is of benefit to you.