I learned the hard way that before giving advise on packs ask what it is going to be used for (specifically) and what season (conditions.... specifically) it is going to be used for....

Otherwise one is just shooting in the dark....
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So for general consumption and not really in answer to your question:

For first rifle elk season where it may be hot or may be a thunderstormor may be a blizzard and you need a place for all your clothing layers, where water is scarce, and where historicallywe have ended up spending the night in the woods with no real camp I use a Dana Designs Astralplane, essentially a Everest pack-in model.... about 7000-8000 cu. in. but sucks up/shrinks/compresses down real good when going towards empty or emptier.

This year, since we travel into and out of our hunting areas in the pitch blackness, I packed my rifle in the back pack (barrel sticking out the top) and used trekking poles which were great in dealing with mud, water crossings, scree, snow, ice, and slick sloping terrain.

Now if you are a summer archery hunter, or hunt deer close to home.... don't really even need a pack at all, just a fanny thingy.