In past Call of Duty: Black Ops titles, unlocking Prestige Mode would set back a huge chunk of your progress in leveling up weapons and perks. That won’t be the case in Black Ops II, according to the dev team.
Specifically, Treyarch game design director noted the following bug from the Black Ops II quality assurance team:
Just got this bug from QA. “Weapon levels are given after unlocking a gun that was leveled up on a past level progression.” +
— David Vonderhaar (@DavidVonderhaar) September 16, 2012
However, it turns out that the bug isn’t a really a bug after all.
In Black Ops II, you’ll keep your current weapon levels after unlocking Prestige Mode, saving you a bit of backtracking and experience grinding. Now, you presumably won’t need to start at Level 1 for your perks, killstreaks, grenades, and attachments.