[Jackarutu]

First turok_t says: “My FPS using 0.25g bastards and G&P 9.6V battery are:”

Then Styrak : “So you're shooting about 350-360 on 0.20's with an M120. Not a "shitting FPS" but yes it's lower than it should be.”

I believe all experienced players and techs will agree that the standard is based on .20 BB’s with hop-up off. Reporting a secondary BB size might be an interesting antidote but it doesn’t really help much to make a comparison to the standard.

When I think there could be a problem with the air seal between the air nozzle and the hop-up rubber I remove the upper receiver and take out the inner barrel and get second pair of hands to hold the hop-up firmly against the gear box and in perfect alignment to the gear box: with the hop-up upside down. Then someone feeds a single BB into the hop-up and we fire thru the chrono. What this does is remove any miss-alignment between the hop-up and gear box that may be present due to fitment in the outer barrel.

If still no joy, then check the hop-up and the position of the rubber in the hop-up. This may be hard to do. The air nozzle needs to make a hard seal against the hop-up rubber.

From empirical experience working with Madbull hop-ups: I find if one gets in a hurry and doesn’t check it is very easy to get a maul formed hop-up rubber at the front of the hop-up when the air nozzle engages. When you look down the barrel from the hop-up end you should see a perfect circle. If you see a distortion in the circle pull the inner barrel back and try re-seating it again.

Hop-up rubbers can get into some really crazy problems. Just recently I got an M249 in with a fails to shoot complaint. Turns out the hop-up rubber had somehow gotten totally pushed inside the inner barrel.

I’m not trashing Madbull hop-ups. I use them on all custom jobs. Once the hop-up rubber is seated correctly they are outstanding hop-ups.