Boy, I'm sure I'll be corrected if I make this statement--and I'm wrong. You don't nail into the grooves, you nail into the top of the tongue. The nail should be covered by the next board. That's the way I was taught to nail down flooring and ceiling T&G. IF you happen to put in a nail and it does not set all the way into the groove, then you cannot put the next board in. If you nail into the tongue, right where it meets the main part of the board, and the nail does not set all the way in, then you can set the next board into place with a piece of T&G board and some persuasion. As far as which guns to use, I've only seen the pro's use a special gun for T&G boards (mind you, this would be for flooring), I've never seen anyone use just a framing or finishing nailer for T&G boards, either flooring or ceiling. Good Luck, David