I want to say that the pin that you have to remove is about 3/4" inch long, it's been a while since I've had mine out.

It's a steel roll pin. A nail may or may not do the trick as it's going to widen the end of the roll pin where the nail is making contact. Ideally you should use a roll pin punch, you'll need use the punch or other tool to get that pin almost all the way out of the grip, DO NOT USE PLIERS TO PULL OUT THE PIN ONCE IT'S POKING OUT AS YOU CAN CRUSH THE ROLL PIN.

The pin may be a little stiff and hard to remove. I had to use a roll pin punch and small mallet the first time to get it out, but supposedly the newer guns are easier to work on...

mines pretty new and it was a piece of work to get that roll pin out. had to nick a punch from work (temporarily) and even with my 8 ounce hammer had a hard time tapping it out. was wishing for my carpenters by the time I got it out.

Check out the thread above on the same topic for tips. Definitely don't want to use a nail 'cause the point will stick into the roll. Ideally use a punch but a 3/32 allen wrench will work also. First time punching that pin out you'll probably need a few tips with a hammer.