Well that doesn't really help him. He obviously knows that they jam.
Mikey, you should search first. This one should be fine because if you search for recon mods, it's not in there. But the Longshot clip mod by TIG is what you're looking for.
The black "Butt plug" as guys I know call it, is just there to protect the bit inside. It is on all new Recons, because apparently you could break the plunger off if you hit it while it was extended in the old ones.
If you want to take it off, its quite easy, just unscrew the two screws on the back of the black thing, and remove it, you don't need to take the rest of the gun apart or anything like that.