Barrel, Bucking, Hop-up

With the hopup, I would instead recommend using the stock hop and doing something like this:

Drill and tap holes in the barrel at the 12, 4, and 8 o'clock positions in three places down the barrel, spaced evenly. Then, warp the barrel upwards in the center with the lower set screws, and downwards at the end, ever so slightly. You may have to drill out the hop unit a bit to accept the bend, but it is worth it. The other way you can do it is to simply drop the end of the barrel down a few mm, that will produce the same effect.

I would recommend ones that don't strip under pressure. I used M5, I think.

You are correct on all accounts; you want the curve to be a parabola, not some weird funky shape, though. Just make sure to drill out the hop chamber, it will allow the barrel to tilt better. Also, until you get it completely figured out, downgrade to ~300 fps. Your results will still be remarkable, but it will be tons easier to tune at that lower fps.

Exactly. I drilled it to about 10 mm, slightly larger than the barrel OD.

I really like keeping my stuff at low fps, no MED (really awesome, don't feel as guilty shooting people in the head at 296 fps as I would at 400+), and then I am allowed to shoot my BASRs in auto . I can also prove to newbs that fps means nothing. I mean, the only gun that I have that shoots over 400 fps is my CAR-15 at 130 PSI (~600 fps!!!), and at that point I hit 120 meters easy... Don't worry, I run it at about 90 PSI, or about 360 fps.

No problem, the more the merrier!