If you want a day pack with a rifle scabbard, look at the Eberlestock Gunslinger II. I have one and it works well for day trips. If you want a nice pack without the scabbard, look at 5.11 Rush series. They make the 'Rush' in three sizes 12, 24 and 72 (hours). A buddy has the 12, when I queried him, he recommended the 24 as the 12 was just slightly too small. The 24 is perfect for a day pack.
If you want one with a scabbard, then you have a couple choices. Eberle stock makes a couple. I think the x1a1 would be the best daypack. But if you want the best and want the capability to pack meat then get the Kifaru Mountain Rambler. It's pricey but it's the best. Depends on what you want and need.
I've been using a gunslinger 2 for a couple of years and I am about to get rid of it. If you weight it down at all, it gets uncomfortable. I typically have around 30-40 lbs in it including my rifle and it wears on me. I think it is a flawed design. When you compare it to a true backpacking harness like on a Kelty or Kirafu pack there is a huge difference. On the Eberlestock, the load straps are useless because they are in the wrong place. They should be angled up at about a 45 degree angle, but they are basically at a 0 degree angle (parallel to the ground). One you load up the pack and put on the waist belt, the weight of the pack wants to fall backwards. I think newer models have some sort of frame in them, but I dont know if it makes it any better or not. I think after my hunt this fall, I am going to look for another pack. The only thing is finding one that has a scabbard built in or some type of system to carry my rifle.