New M4 Hop-Up Unit

[Jun Wen]

Some of you guys might have noticed me at Rubber Ducky messing around with my inner barrel. After quite a few odd problems, I've decided to just pick up a new hop-up unit. Does anyone have suggestions about which ones work the best? The CA metal ones seem to require modification of the reciever to fit, which makes me feel slightly uneasy. It looks like Systema and G&P also make metal hop-up units, but I don't if they're any good or if they definitely require reciever modification. Any suggestions would be greatly appreciated. Thanks.

[OverKill]

I can let you know about the systema one in a few days as soon as it gets here. if it needs to have the modification done.

[Tank]

If you have a stock Marui body...Then yes you have to modify the lower receiver for the one piece hopup to fit/work.

The Systema & G&P are both quite good units.

[bear]

I have a systema in my M4 you works fine, but you do have to cut a chunk out of the lower reciver to fit it.