What other features do you need from the pack? How much capacity? What’s the application in which you’ll be utilizing the pack? How quickly do you need to access the rifle from the pack?
These answers will guide recommendations for which pack. For example, I carry my rifle in my pack during a 12 day hunt, for which I use a Mystery Ranch 6500 pack with NICE frame, in conjunction with an MR Load Sling as a rifle carrier. This is a huge pack, capable of transporting everything I need to make it 12 days on a remote mountainside and includes modularity to haul meat on the frame and load sling when big game hunting.
Alternatively, I also carry a rifle in my pack during precision rifle matches at certain ranges where we might walk 3-4 miles each day between stages with ~20lb rifles, support bags, ammo, and gear. Don’t need the capability to haul meat, don’t need the capacity to haul camp and 12 days of clothes and food, just need room for ammo, support bags, and limited match gear. But it does need sufficient organization to store several small and administrative items like rangefinder, weather meter, chamber flags, data book, etc. For this, I have an Eberlestock LoDrag II. Much smaller than my mountain pack, but plenty big for the purpose, and still has the ability to haul my rifle and all of my gear.
Personally, I believe a person gets what they pay for in packs. Kifaru and Mystery Ranch are the two “top line” packs I recommend for external frame packs. Eberlestock is more affordable, and great quality for internal frame packs. Eberlestock makes a great variety of weapons carry packs in various sizes.