As I said earlier, I use a Spec-Ops brand THE pack. This is how I load it;
Main compartment I have a small STR8laced bag. I seldom use it, but it's there if I need it, on the very bottom. Depending on weather, or what caliber I'm shooting, I either have rain gear or MTM ammo boxes at the bottom. The ammo boxes are the 50-round type, flip lid. I can squeeze two at the bottom next to that small bag. Typically you run around 100-rounds per day at a match. If there's a higher round count, I'll also load my magazines, and normally carry three AICS 10-round mags. They go on top of that small bag. Some matches, I've started to use those bullet binder type ammo carriers. They normally hold 40-rounds each, so I carry two of those, in addition to loading up the mags. Again, depending on the weather, I'll keep the rain gear at the very bottom, with the bullet binders on top.
At this point, my pack is half full, and on the top half I will keep my Kestrel 5700, Terrapin, snacks, maybe squeeze a bottle of water or Gatorade to one side. If there's room for it, I'll fill the bag the rest of the way with my Traust rear bag (6x9x4"). Also inside the main compartment, there's a little mesh compartment that holds my data cards, another Kestrel (2500), and countdown timer.
On the outside of the pack, There are two zippered pockets, one over the other. The bottom pocket I put things I don't need that often like gloves, leatherman multitool, a small thin nylon wind shirt, wash cloth, and Velcro straps.
The top pocket I have my binoculars in for quick access.
On the outside of the pack, I clip my Weibad pump-pillow, and a clear map case that holds a paper hard copy of my Dope, just in case the battery dies in my Kestrel, or I don't have time to mess with it.
I also have attached to the top pocket via PALS webbing, a Velcro flap Admin pouch that holds pens, markers, grease pencils, ear plugs, chamber flag, and an Allen wrench in case I need to make a scope adjustment.
I usually carry my rifle slung across my chest, and carry my tripod in my hand. If it's a real long hike, and I know I won't be needing my tripod, I'll strap it to the side of my pack.
Oh, forgot to mention, on one side of my pack, I have a nylon dump pouch with elastic opening, held in place by the compression straps, and dump my brass in there after shooting each stage.