For my magazines, I have RAID modded (Process of taking off the top chest pockets, moving them to the arms at an angle, and moving the bottom pockets to the chest) my BDU. I can easily hold 2 magazines in each pocket of it on my arms. My chest pockets hold my maps, compass, and face paint.
Something I have found works is taking an Eagle 3 Day Assault Pack III (With molle). Spraypaint it, burlap cover it, and just all in all camo it up. You can wear on your back while you are crawling or walking, but when you are stalking in a low crawl you can strap it onto 2 carabiners on the back of your belt, it takes a little to get used to, but detaches quickly. Works wonders for multiple shooting positions besides prone.