I've also looked really hard at this pack as a hunting system but to me the pack wasn't rigid enough for heavy loads. That is until now, It looks like they have made some updates to the design of the Gunslinger II pack, giving it a more stable platform with heavy loads. I copied this from snipershide:
Instead of me going through these new features, I'll just copy/paste the message from Eberlestock
The G2 Gunslinger ll has been one of our most popular and bestselling packs since its release in 2009. Over the lifespan of this pack minor changes have shaped the platform and transformed it into a ruck that has served a multitude of purposes. From a combat ready assault pack to a remote hunting survival pack the G2 has proven itself as a leader in the mid-sized tactical and hunting markets.
Today we would like to introduce you to the next evolution of the Gunslinger II. The first enhancement to the pack is our new Intex II aluminum frame. With the addition of this frame, the user will now be able to utilize a solid platform thatís designed to add strength and stability to the pack. This system is designed to be interchangeable with an alternate frame (coming soon). Or, the frame can be completely removed (ideal for using the bag as carry-on luggage), allowing the pack to revert back to the traditional G2 platform. This new set of features is going to allow the user too completely re-think what is possible with a G2.
The other two additions to this pack include: a redesign to the back padding and new placement of the load adjuster straps. By re-configuring the padding on the back, we created a system that covers critical comfort points on the users back, allowing for maximum breathability and optimal contact points; the padding is more efficiently placed and is comfortable and stable with either direct-wear or with body armor. The new placement of the load adjusters allows the user to compress the scabbard compartment in a way that is in balance with the load on the pack. It is a simple and efficient way to dampen the movement of a weapon being carried in the scabbard.
-- We no longer plan to make the G2H in our hunting camouflage patterns. For customers interested in a similar pack in hunting fabric and camo, we recommend the M5 Team Elk pack.