I highly recommend BB Bastards. I've shot nearly 10k rounds through my gun without one issue. I've cleaned my barrel once....i know bad me, but there's was almost nothing to clean. The silicone dampened piece of paper towel i used came back maybe one shade darker, lol. Could hardly tell it was dirty.
During some indoor games, you can pick up a handful of BBs and quite easily point out the Bastards. They are very shiny compared to most brands.
Hmm, speaking of which i'm on my last bag, time to put in an order!