Broom handle always worked well for me.
I used to use a broom handle. Now I use a 2' piece of 3/4" EMT (steel electrical tubing). OD is .94 inches, about perfect for alignment. You can buy a 10' piece at Home Depot for $4, or ask your electrician buddy for a left-over scrap.
That said, almost all my guns are mounted with Weaver-style rings and bases, a much more reliable system.
