Would really appreciate some help with this.   I want to remove the Urbino stock from my M4 and put the factory non-pistolgrip stock back on.   I popped the butt pad off and started to unscrew the big screw inside. The one that looks like this:     [ATTACH=CONFIG]1043[/ATTACH] Instead of the screw unscrewing from the end of the recoil spring tube and so freeing the Urbino stock, it instead undid the endcap that screws on to the end of the recoil spring tube (the screw for the stock