But, to help answer your question, here is what I use for our club's 3-gun matches.
Pistol - Glock 34 - Mags on belt - 2 min.
Rifle - S&W M&P15 with Red Dot - One mag on belt in comp-tac holder.
Shotgun - Win 1300 Defender - 6 shot Tac Star on gun, 8 shot Blackhawk arm ban
I usually wear pants/shorts with big pockets, just in case I have to take more ammo along than I can put on my arm/belt.
Here is a vid of me in one of my first 3-Gun matches, might be different than what you may run, but it could give you some ideas.
![coolgleam :coolgleamA:](./images/smilies/coolgleamA.gif)
[youtube]http://youtube.com/watch?v=OL58GqZ1SOw[/youtube]
Also, I always take 2 to 3 times more ammo than recommended for the match, just in case. You might have to redo a stage for various reasons, and running out of ammo stinks.
Furthermore, check out the 3-Gun forum on Brian Enos's forums, LOTS of good information there.
http://www.brianenos.com/forums/" onclick="window.open(this.href);return false;
Ryan