First off, Congratulations on the fabulous hunt. Junction Tx, is conducive to such game. Excellent job.
260
I have a 260 Model 7 in the 18" barrel. It was one of the first ones to come out. It took me 6 months of work to get where I wanted to be. I finally stumbled on the perfect load for MY gun.
I use the 140 grain Nosler Partition, with 45.5 grains of RE 19 . This produces one hole groups at 100 yards. Now remember that it is a 18" barrel so I have to limit it to three shots.
Suggestions have been several other powders, with the 140 grain. The 120 grain Nosler has worked good on Deer, but the 140 takes care of Hogs and would be a better choice for several other species.
Remember this also, keep in mind and pay attention to what twist is in your barrel. Mine is a 1-9 This is what Big Green chose. You may have a 1-8 which is better especially for the heavier bullet. I know that you can use other powders, but for some reason it worked good with my gun. The Nosler 120 grain shoots three shots that can be covered with a dime. Same powder, just different amount.