Yeah, the k612 has a lot going for it
For your gun sounds fatigue... Yeah guns are usually loudest in every game. However, I also recommend turning off Crystalizer in the Recon3D, it's a fatiguing combination with AKGs, and check out my Recon3D USB review (in my signature) for a few recommended settings. You can tweak them afterwards to your taste, for example some people might like a small amount of smart volume to make loud sounds a little softer and quiet sounds a little louder (but don't overdo it as that might mess up the soundstage depth) or using the EQ to tame a frequency that feels too aggressive for you. The Recon3D has a lot of adjustability (gotta plug into PC to adjust it), and that's a powerful tool I recommend you take advantage of.
Enjoy!