Oxberger, this year I used a game cart to haul 15 gallons of water up above treeline on an old jeep road in a national forest, and then used it to haul gear and deer out. It worked awesome, and really was the only way to hunt this particular area and stay high the whole time (without horses). It was an area that I had backpacked into over the summer (about 10 miles in) and I figured since there was a two track for half the distance that I should see how it would work with a cart.
I hauled the water 5 miles and 3,000 feet up to the wilderness boundary the week prior, chained it to a tree, and then carried the water into our camp area (in the wilderness) on my back. It was extremely difficult (took me twice as long as it normally did to get in) but it got the job done. After we shot a deer, we packed the animal and camp to the cart in one trip, threw it all in the cart, and rolled it down to the vehicle. It didn't make things super easy, but again, it worked. We really wanted the cart in case we shot an elk so we'd have two or three relatively flat trips each to the cart and one downhill. Be prepared--wrestling a heavy cart downhill uses an entirely different set of muscles.
I got the cabela's super mag on craigslist for 50 bucks (it had one bent wheel) and it worked like a charm. My only advice would be to buy extra hardware (nuts and bolts, etc) and ducttape them to the frame of the cart, because they'll vibrate out several times
View attachment 11256 over the course of a long and bumpy haul.
I (hopefully) attached an image of the haul back downhill. The cart has my deer and gear in it. If you have any questions, let me know