Gun or Compressor not working properly

I have a Power G Plus 2 HP Compressor and I've just bought a Dewalt D51276 34 degree 15 Gauge Nail Gun using 32mm X 1.8mm nails on a 34 degree angle but the nails are sticking out a quarter of an inch I've tried altering the pressure but it makes no difference. Could you please sort this problem out for me as I'm going mad trying to sort it myself. Kindest Regards John A desperate Amateur