Pete/NY,
Contact Remington regarding the use of the 7600 magazine in the 760. As for a load to use, 30+ years ago I hunted with an elderly gent who used 130 grain Hornady bullets over a DuPont IMR 4350 powder load 1 grain under the max in the then current Hornady Manual. He found out that Full Length sizing dies were a must and that they required careful adjustment per the RCBS instructions. All his shots were from a tree stand at undisturbed deer (at least they were in this state when he got to shoot at them) standing or slowly walking. His farthest shot was about 80 yards, and most were much closer. As I helped drag and skin all his deer, I can report that all bullets penetrated completely. The bullet was quite disruptive, even upon entering. He never had to take a second shot, and all the deer expired almost upon being hit. There is a caveat here; none of these were snap shots in thick brush. His tree stand had very clear shooting lanes and fields of fire, so I cannot report on how this load would be in the brush.