The question is whether or not you can over-upgrade. Possibly, as far as functionality, but not when the cool factor is considered. There are such a vast number of possible gun upgrades, but these are the 12 best upgrades we found.
1. Custom Fluted Barrel
This is one of the best barrel upgrades on the market. It comes in various lengths, but the best for the money is this 16″, spiral-fluted, bull barrel. This piece of beauty is made of 146 stainless steel. It is produced by Rock River Arms.