I was going to buy a bolt but was warned off them so I bought a g&p force recon m4 which has a good recoil system for around the same money as a bolt.
My mate couldn't put it down when I took it to the gun club(I think he wants one hehe)
Latest update.... Popped the 6.08mm barrel in and fitted a namazu firefly flat hop nub and the gun is still doing 370-380 so it seems like the hop rubber is very effective.