ziGzaG's tactics page has been updated with three new articles What are they? "Understanding the MP5 Navy", "Controlling the de_dust Underpass", and a special guest map guide, "de_inferno by Deean". Here's a bit from their MP5 Navy tidbit:
Close RangeRead the rest here. In case you don't know, ziGzaG's site is a great resource.
Even if you don't burst, the MP5 Navy is surprisingly easy to control and it's bullet spread is rather small. When using the MP5 Navy at short or no range your best bet is to hold down the trigger and 'pull' the bullets where you want them to go. Spend some time drawing shapes or writing your initials with the bullets to get a good idea of how to gain control of this awesome tool.
Medium Range
I like the MP5 Navy the most in medium range combat! At a medium range I found that the fastest way to get the kill was the 'Pull to the Throat' method. Some other good ideas are to burst 5 shots or maybe even 8, or to aim for the enemies head (you should be aiming at the head anyway) and shoot 3 shot bursts.