No personal experience, but here's a very interesting thread about it:
http://www.ar15.com/forums/t_6_42/39...llet_Test.html
"I was able to put 500 rounds of cast bullets through an AR-15 without cleaning it and did not have any problems or malfunctions at all. The test showed (to me at least), that AR-15's can be made to work consistently with cast bullets. In regard to accuracy, I didn't see any significant change in accuracy, but I wasn't really testing for it."