Happened to me a while back but was even weirder, i had a uzi jumped of quarry and hit the floor and it turned in to akimbo p90 but with only the right gun lol, when i aimed it just slightly went in and made the gun bigger, i could kill people with it i died a few times and it wouldn't go i then decided to throw a stun and it vanished... i was like wtf
At first, it may seem like a harmless animation glitch but like Jonneh said, you may be able to get it to benefit you. Add more attachments, change attachments on the same class in-game, and if we experiment more, it could be possible to completely transform the gun and mod it as we like (Actual scar with p90 size clip)
The same thing happened to me. I was using a barrett but it turned into a m9 with tac knife but when i scoped in zoomed in like a sniper and fired like a barrett