[Eeyore]

Originally Posted by Mr. G36!

Hey, all. Quick question: Is it possible for the inside of an M4 lower receiver to be too tight to allow the gears in the mechbox to spin?

See, I replaced a Jing Gong M4 lower/upper receiver and pistol grip, and threw in a Systema mechbox. At first, the gears would just either squeal, sounding like the motor wasn't raised enough, but raising it eventually just locked everything, as it was too high. Now, I've checked shims and they're prefect - one thing I do know how to do. I tried different pistol grips to make sure the one I initially used wasn't just off on an angle or whatever, I checked the barrel and everything associated with it to ensure it was aligned properly and that it wasn't canting the mechbox slightly, and the battery is good.

Now I've built G36s from scratch and made works of art, but these V2 contraptions are still sorta new to me. I figured that I should ask before I start filing out the inside of the lower just in case that's just a really bad idea.

Thanks!

I find Systema gearboxes slightly larger than other brands. Mine barely fit into a KA receiver.