It sounds like great fun to me!
They all burn barrels and the problem can be exacerbated by shooting them with a hot barrel... but who cares anyways? He can buy another one or re-barrel it.
If this rig is shot and cooled between shots or general hunting shooting, it should hold accuracy for 1000+ rounds. It wouldn't make the best prairie dog rig with high round-count rapid-fire rate but it would be awesome for chucks, deer pronghorn, sheep etc.
Shooting 50 rounds per year (after all the load development) this rig is good for 20+ years! That's way more actual shooting than most MMer's will do in a year with a single rifle after development.
Oh so many fun toys and so little time/money!
Zeke