Have you shot it since you bought it? I've done no mechanical mods to mine and can put 140 out of 150 rds in the target at 100 yds rather quickly, what else could I gain? I found an AR place and all they talk about is hot rodding their AR's like they're 69 Camaro's. Needless to say, lots of cowboys over there, braying like donkeys about the gadget they're saving up for.
Is there something wrong with the upper now?