We add pork fat or trimmings to make sausage, beef fat or trimmings to grind burger. If you don't intend to form patties and make hamburgers, don't add fat to the meat, just to the pan to prevent sticking. I think deer is too lean to make a good burger without added fat. JMO, Mike.
Way to go, son. Nice shot. I will tell you however, that a missed head shot sometimes takes off the jaw, and doesn't kill the deer, except very slowly. Where I live, the deer have become nuisances, so no one cares too much. Varmint killing. Mike.
Check out this address:
http://www.accuratereloading.com/260rem.html
These are some loads developed for a custom rifle in .260 with a 28" barrel. You may not want to go quite so long for portability or handiness, but this caliber seems to like slower powders, so a longer barrel would be an...