After reading old damage calculations in wiki I realised there is a problem with Combat Shotgun. Not the overpowered/underpowered problem mind you, no the problem is that it the best effect isn't achieved by using it as it should be used. The "standing pump" has a time of 0.2 second - little known fact, but still an important one. Also that 0.2 sec is added to the special reload time. BUT if you have exactly 0 shells and load one normally you ignore that 0.2 second. In result doing "Fire, Reload, Fire, Reload" routine is more effective than "Fire 5, Reload 5" one, because the former gains one free second per 10 shots fired - this obviously isn't meant to be.
My fix suggestion is a simple one. The combat shotgun has already some variable that checks is a shell pumped or not, right? Then it should preserve the "empty" state if reloaded normally - essentially if someone loads a single shell he should still have to pump the shell - the most obvious way is just adding the 0.2 extra time to loading time of first shell. Also special reload should check that variable too, and add the 0.2 second only if the shotgun is unpumped.
Lastly I think it might be usefull if comabt shotgun status could be displayed somewhat like that
Combat Shotgun (6d3) [1+4/5]
..where the 1+4 wouild mean "one shell ready, 4 more in magazine" - personally I sometimes forget if I have a shell pumped or not - what do others think?