ACP Delrin Low Blow Bolt
CORE Feed Neck
J&J Edge Elite Barrel Kit
VL Eye Force hopper
Pure Energy 72ci 3000psi
Anything of good quality. Meaning...nothing oblonged or dimpled
Your wondering how rifling could be a strength and a weakness. I will tell you... 1st, this is a good barrel. Quality feel and look. Looks great on the gun. It's relatively quiet, as quiet as an MR1 is gonna get. Now to the rifling, as long as you are shooting perfect paint the barrel is as accurate as anything I have ever used. However, if you are using paint that is even slightly dimpled or out of round you are going to be shooting everywhere but where you are aiming.
Once again...As long as you are using great paint, this is a great barrel=9. Not great paint, probably the worst barrel you've ever seen=4