When I look at my state's building code (massachusetts) and see nail sizes for given applications, the sizes sre specified by d size, no big surprise. So for example for a 2X4 stud to a bottom plate has (2) 16D required.
From looking at a chart a 16d nail is .162" diameter X 3.5" long
It appears that nails for nail guns aren't sized the same. From looking at available nail gun nails at Amazon (thinking of getting a Porter Cable FR350A full round head nailer) I see for galvanized 3.5" X .131" diameter. None of the nails are sized by d number and all of the nails of a given length are smaller in diameter. Heck I don't even see anything larger in diameter than .131". Also I don't see any nails 2.5" long (to correspond with a 8d nail). I see 2 and 3/8 and 3" long but not 2.5".
So my question is how does one relate nail gun nail sizes to conventional D nail sizes for the sake of complying with building code? Do I just pick a nail that is the same or greater length and the smaller diameter doesn't matter (doesn't seem right)?