[Varjeal]

Greetings.

I've a VFC M4 that I've recently installed with the following:

SP120 Lonex gearbox
Lonex A-1 motor
SMU-non ab
7.2V lipoV battery or 9.6V nunchucks are all I use.
363mm 6.03mm VFC Psalm barrel (yeah I know its gimmicky but I wanted to try it out.)
Varied between madbull 3in1 hopup, prowin, and stock. (having feeding issues but that's for another topic)
Black madbull bucking w/shredder nub


The story is that I need this to shoot a maximum of 420 fps and I'd prefer to stay closer to the 400-410fps mark. The advert for the mechbox states an fps range up to 440, and after a shim adjustment and compression check (compression was actually quite good) this easily attains the advertised maximum fps and more, which is a problem.

Second part of the equation is that the motor *overspins* (corrected from previous) (ie locks up solid) with a 110 spring after only a half dozen shots, so simply down-grading the spring isn't going to work with this combo.

I'm looking for possible solutions and need some advice on what is the most practical and reliable method of "down-tuning" to achieve reliable operation. I'd really like to keep the A1 motor in the equation if at all possible.

Thanks for your time and consideration.