with my RDIAS, I'm happy to get a 10rd burst before it jams. The rear lug of the AR57 is thinner than some of my other uppers so that little bit of slop between it and the RDIAS is my issue I think. With a friends Colt registered receiver I would say it runs 98% with only 1 jam every other mag and those were full 50rd mag dumps :)
Hopefully this pic comes through of it with my Spectre II on the AR57, the gap between it and the handguard is irking me though. Even though I won't use it often at all I think I wouldn't mind getting something that fills it out more.