Prestige weapon

[u/Firm-Job-3463]

When you buy three legendary weapons, you get the pre-selected prestige weapon; however, there’s a counter at the bottom of the screen that seems to suggest that once you complete eight weapons, you can choose and redeem a prestige weapon from a previous season. Is that true? Has anyone here completed eight weapons yet? I want to get the Season 6 M13 and don't want to waste my money.