To get this Trophy you have to buy/sell any type of Ammo at the Exchange kiosks.
An easy place to do this is on the Chapter 'Polis', make sure you have close to 500 Military grade rounds. After the first part of the chapter while you are waiting for Miller. go to the Exchange Kiosk and sell all your ammunition (will go towards the total 500 Military grade rounds) and then buy as much ammunition as you can. Once that is maxed out then sell all the ammunition so you can purchase more.
After doing this a few times at the Exchange Kiosk you will get the trophy. From what I have read you cannot reload the last checkpoint. For more help check out the YouTube video for help.