I don't think they'll chop (well, maybe bobble the ball stack pretty hard, hard to say), but shooting .50 out of a .55 cal barrel is like shooting .68 out of a .73 cal barrel. Getting full field velocity will be really, really difficult.
The Maxx55 was the first attempt at making a new player friendly version of paintball. They didn't hype is as the "next big thing", or claim it was going to "take over the sport", so they were more honest, but it makes you wonder if that honestly was the reason for their downfall. Something to ponder.
Anyway, converting to the smaller caliber may be more hassle than it's worth. They did make a .50 cal Freak barrel who's inserts might be used to step down the barrel (anyone know the wall thickness of the assorted freak inserts off hand?), so that's something to work on. You may be better off selling them as a collectible oddity.
David Johnson, AKA Fubarius.
Nunquam emere potes facere