We have an 18cu ft upright freezer, it currently contains probably about 60lbs ground venison, plus roasts and cuts from two deer, but also something like 1/8hog, 1/4cow, bunch of fish and say 1/2dozen prepped dinners. You could fit like 5or6 processed deer I bet in the average chest freezer which would be a great many burgers, say 3 or 400.
I found on a quick search that 0.5lb ground beef is 14.44cu in. So if we're calling all red meat the same density, and a loose packing factor of 0.75 it looks like about 1615 1/2lb venison burgers in my freezer which is quite a bit more than 400.