This looks really great, and shows a lot of polish in its interface. I liked how you had different preset ways of filtering the data (SMGs, Rifles, etc), as well as linkable results pages. Being able to select armor and hit-locations seems to just be a scaling factor, but also was a neat touch.

I think there might be some value in adding a duration slider (as an alternative to shot count). Because most items you're comparing has varying rates of fire (e.g. P90 vs UMP45 vs Mac10), the slower weapons will often show more "damage" (over N shots), whereas the DPS might be similar or vary a lot.

It might also be interesting to have weapon selection filters based on cost -- e.g., comparing rifles and SMGs of similar cost, or things you can buy on the first or second round.

Edit: I also just went to the advanced charts section, encountered your buy-me-a-coffee link. While I personally don't like signing up for additional tiers of access, I think this was a very nicely done way of doing so.