Here's a trick that allows you to unlock any weapon upgrades for free in GTA V. The trick lets you 'buy' any weapon upgrades, but the money you spend is returned to you and the upgrades will remain unlocked.
If you're looking to jump ahead a bit in the weapons game, this may be of interest to you.
If you have any weapon upgrade hints, tips or tricks for GTA V please post them in the comments below. Thanks for your contributions and for visiting the site.