What is good accuracy value in a .223 A3 upper?

[bushmaster1313]

I would like to upgrade my Bushmaster XM-15 E2S from an upper with a light 16.5" barrel to a more accurate bull barreled upper.

Should I go 18" or 20" and which brand is a good value?

Who sells them?

 

[browningguy]

I have one DPMS bull barrel and it has always been a good, though not great, gun, it averages around MOA but even with a 9 twist it really prefers 52gr. bullets.

I also have a new 18" ATH upper from RRA and it is superb, shoots everything up to the 75's I have tried in it very accuratly. This has the RRA Heavy Barrel, a little less than a bull barrel but more than a standard weight barrel.