What year is the Gun ?
Unless I am mistaken, and please somebody set me straight if I am, the 09-10 G&G, V2 guns are the only one with the new re-enforced GB as standard.
If your gun is older than that, you may be heading for trouble by installing a M130, I take it your gun is currently shooting around the 1 Joule level ( 330 FPS ). The standard GB from G&G is safely rated up to the M120 level 1,44 Joule or 393 FPS, if all tuning and mods are done correctly, a M130 would bring you outside of that range considerably, 1,69 Joule or 426 FPS ( by the way, also outside your fields allowed limit. )
as an after note, the standard gears from G&G will not handle the M130, you will tear teeth of the Sector Gear, and in a worse case, destroy the entire GB.
Subject: m130 help 
Thu Aug 06, 2009 3:20 am
(but im tryen to learn more about the mechanics of airsoft guns so i can do this with ease cause im wann get serious bout airsoften 
) so i needs some help guys.i was wondering that since i got a m130 spring would i have t upgrade the gearbox or the gears and other internals to let it work withought damaging my g4 socom.
