PGC Gear Box Conversion Kit Set for TOP MP-40
 

1

http://www.airsoftcanada.com/SpringChart.html

-Cheese

http://www.arniesairsoft.co.uk/?filn...ring_guide.htm

edit: rats, beaten to it!

HAHA I won the "Post the spring guide" race. (If only by less than 60 seconds.)

-Cheese

1

100 less wear and tear, around 310 fps.

130 overkill and likely kill your mech, around 450 fps.