by Flak » Wed Jul 14, 2010 6:30 am
The spring guide keeps the spring from bending upon compression in the gearbox as it cycles. In conjunction with the hollow part of the piston, it contains the spring linearly to have the gearbox rely on its structural integrity rather than its screws.
You skimp on the spring guide, you run having the spring bend out the side of the gearbox, push a piston out of line, etc. It won't necessarily affect your shooting performance until something like these happens from not having it.