2 nails shoot at the same time

No, It uses Clipped head nails.

The manual for your gun specifies 34-degree nails from 2 to 3 1/2 inches long. 28-degree, wire collated nails are a Stanley-Bostitch thing and they only work in their nail guns, they will not work in your nail gun. You need 34-degree, paper-tape collated nails. I know Senco framing nails will work in your gun and I think Duo-fast makes 34-drgree nails but check that before buying them.

I would look at the nail collation and nail angle first. If both OK for this tool, remove all the nails and air hose. Bounce the tip and see if the driver falls down on its own and if it does the o ring is worn and would need replaced. When inside the tool look for other wear items.

Yes, just disconnect the air line and get in there and dig them nails out, don't wait for somebody else to work on it. Do it yourself. The front of that gun should lift up and expose the nails coming through, pull them out with pliers, make it clear, then reload and fire it back up and see what happens, a lot of times the generic nails will clog up.

the first thing that i look at when a gun is double shooting is the nails. if i have the right nails then i check the driver( part of the gun that hits the nail) if the driver is fine( not bent or broken or worn) then your nose( chamber that holds the nail right before being shot out) is worn or broken. either way to answer your question , no , double shooting is not only dangerous but a complete waste of time, ps rate , tks

This gun takes 2"-3 1/4" .113" - .131" Paper striped 34 degree clipped head nails.

This is the Tool Card provided by Hitachi. Follow link:
http://www.hitachipowertools.com/product/files/pneumatics/framing_nailers/NR83AA3toolcard.pdf

I worked at at tool rental center while attending college and learned from the old tool masters about nails and nailers. Rental stores have many different brands of nailers to rent and customers would bring their own nails of all brands. You will notice on the case/box that your nails will /should work on many other brands however the degree or angle of the nails is not always exacly as stated on the box. You should check with protractor the exact angle of your nails and also check the exact angle of the nailer. Use straight edge on travel path of the piston and another on guide rails to check angle of the gun. You will discover that all is not as stated as in a perfect world. If the angle is off slightly, the head of the second nail will get into the path of the driver. This happens mostly with clip head because the nail heads are so close together. The full round head is spaced further apart with less jamming. If angle is off slightly, take a look at other brands of nails with protractor in hand, the angle will be different slightly or choose a slightly thicker nail. Look for the nails to fit with bottom of nail hitting the barrel first. This will move the head of the nail slightly away from the center line. Finally do not release pusher with force as this will jamb nails closer together. Good Luck!?

Make sure to blow out the magazine where the nails load, make sure the spring tension on the nail clip is working properly, make sure you're not holding the clip somehow with your off hand so the clip can't feed correctly.

The dial on the top of the gun is most likely the depth adjustment for the nails, this should solve the driver damaging the work piece. Make sure the nails are the correct guage for the nailer you have.

This happens to my gun too. You probably need to oil the gun once in a while. Here is how you fix it:
Disconnect the gun from the compressor first don't wanna get hurt or anything like that. There is a pin that shoots the nail out well that pin is jammed so what you have to do is push that pin to the original position. using a flat head screwdriver would help you to push that pin back into place. Let me know how that turns out please. I pretty sure that is the problem with your gun. Make sure you lubricate the Nailer once in a while.