I'm using the Type 25 and it's stuck on Diamond. I've been playing ranked matches and I still don't gain weapon xp on it. I'm ranked Pro II.
Any ideas, or should I just say screw it and level up another gun...
None.
NudeRaider -- Also I like how someone quoted you a few posts down and there you can still your old username.
NudeRaider -- Neither did I.
I tried to link a Blizzard source but I think they eventually took it down for some reason, so I was happy to find it here. 
O)FaRTy1billion[MM], Mr.BurnLiquid,
Excalibur