Shims, Springs and gears!

Hey guys,

Looking to fix up a buddies gun, need some help on shims, sprigns and gears, the gun in question is an Elite Force M4 Carbine, it was all stock, he broke it by pulling on the trigger when it wasn't moving due to a jam and the gears from the spur broke the guide gear that pulls back the spring, I want high quality stuff, i'm buying two sets of them and price doesn't matter. He doesn't run LiPo yet, but I want him to down the road, so something that'll hold up. I'm thinking a 2 and a half joule spring.