I've noticed that my weapons have been leveling up really fast. Much faster than they should be, in fact. They're at levels that they hadn't reached previously with the heat I've collected doing runs in the Clockworks. Then it hit me:
The weapons that I've equipped go up one level automatically after you've finished a level.
At least, I think this is what is happening.
I mean that the heat I get (even with an amplifier) won't fully fill the heat gauge, but when I see it level in the next depth, I find that it's already reached the next level (i.e. X weapon will be lv. 3 in one depth and remain lv. 3, but will already be lv. 4 when I go to the next depth).
EDIT: Oh, well, must have been just me. Careful observation has given me reason to believe that I am paranoid.
Check that you don't have any heat amplifiers running for a start. That'll make your heat gained rise. Also, your heat is going up quicker than you think it should be right? I wouldn't complain ^^