JamesAirsofterAgent

ZCI rotary hop + Maple Leaf rubber + ZCI or AOLS barrel is a good start.  You can put them together as a unit so even if you get feeding or other misbehaviour, you can just split the gun and drop the original combination straight back in without missing a game.

I run the combination above in my M904. Works like a laser once breaking in the rubber. Make sure to get a omega nub or similar too.

Its important to note however with that combination you will have feeding issues without shaving the lip of the rubber a little bit. I was having a bit of a headache with it as I don't have the sanding tools to do a "perfect job" however I would recommend using a cheap razor and shave the lip down bit by bit. Testing if the bb's pass the drop test after every couple of passes. Then once it passes the drop test put the gun back together and test with a mag