Check the pressure treated fastener ratings. A lot of the latest PT formulas aggressively attack uncoated steel, so either epoxy coated or hot-dip is usually specified. I have yet to see a proper hot dip nail for a framing gun, but I admit I've not looked very hard. I use regular loose nails with a palm nailer, but for structural stuff I usually go straight for carriage bolts. Directions often say to use lags, but I can never tighten those later when the heads loosen, the threads will be stuck in the wood. At least with a carriage bolt I can still snug the nut a year or two later. I know really the wood will keep swelling, crushing the fibers, and shrinking again and never really be tight so a lag would end up exactly the same, but I feel better being able to put a wrench on it.
Once you have had a nail pull out once and driven it back down, the wood fibers will never grip it again and it will always give you trouble. I have pulled 8d to sink in a 10d or 16d, but that starts to look a little silly on holding down decking, and the points start sticking through.
If you REALLY want to use nails, you could go back to historical practice for nails that won't pull out...drive the nail all the way through both materials, until the amount sticking through and the amount left to drive is about the same (1/2" to 1" on each side is good). Bend the point over perpendicular to the grain. Drive the nail through the rest of the way, then bend the point over again so the point enters the wood pointing back towards the head. This is a "clench" or "boat" nail. Or just use a bolt...