well if you're sub 350, I cannot recommend a Tanio Koba barrel enough. anymore than that and using C02 I'm assuming, I'd just polish the stock barrel (if tm). I'd hazard a guess the accuracy is mainly hop based. Feel free to PM me, I've built 2 x mancraft rifles on 2 separate platforms
Why not go down the R-hop route? failing that Maple leaf are good. if AA you mean reaps....they suck....epically. if that's what you're using now, then I'd attribute your lack of accuracy to that.