My Accuracy Systems improvements include:
750" x 18.5" UMSS barrel, Trigger work 3.5#, bedding the stock, new handguard for the thicker barrel, new tuneable gas block for the thicker barrel, machine work and stock fitting. Sub-MOA accuracy guarantee @ 100 yards. Extended magazine release, red Firesight front sight, ghost ring rear sight and urban brawler rail.
I've been shooting it in 3-Gun and am very happy.