1/8 " tool steel stock makes a nice solid rib for a 22 bbl I have done 2 of these on 22 shot barrels. You do need a milling machine and some basic machine skills. It will take a little time as you will need some fixturing. Think twice and do it once.

There are some throwers on line that you can throw ritz crackers with those and or butterflys make demanding targets. Mind your downrange stuff to keep out of trouble.
Good fortune with your project.