HP,
Did not realize you were handicapped.
Shooting with a snub-nose and a red dot to boot. 3/4 is a pretty fair group under the circumstances you find yourself in.
A few years ago while building a fast twist 22-250 XP silhouette gun, I talked to the folks at Hogdon about best powders. They told me that their best powder for the 22-250 and similar capacity cases was H-414. I bought some of the powder for the 22-250 and then decided to give it a try in the 260s. H-414 produces about the fastest velocities and the tightest groups that I have ever seen posted anywhere for the 260. The powder works well in barrel lengths down to about 14 inches.
Years ago I started loading the 87 grain Sierra in my first 6.5x06. I then loaded the same bullet in my 6.5x55s and my second 6.5x06 and then on into the 260s. The bullet is just amazing in how well it shoots and on varmints, its effect. If you shoot an aluminum soft drink can full of water, when you find the pieces, the jacket makes little holes in the aluminum back side! The bullet actually explodes inside the can. If you shoot a gallon milk jug at 3500, it will shatter the entire jug, including the handle. A chest shot, big chuck, has only feet left in the skin. A crow at 200, turns into a puff of black feathers. The 87s not much good on anything but varmints, but very destructive.
Many powders will give you .75 to .50 groups with the 260. However, H-414 is the only powder that I have seen that will give groups down into the .100 to .150 range with the 87, 100 and 120. If you have the chance, give H-414 and the little Sierra a whirl, I think you will really like the combo. That pictured group was shot with the AR-10 T and a Medesha upper (1-8 twist 24 inch Kreger SS, fluted, match barrel) after I throated the chamber for proper bullet seating with the 120 Sierra (BT top at neck base) so it would feed properly in the magazine also. The load was 48 grains of H-414 with the 120 Sierra HPBT MK. Bullet set .003 off. The group measures .130 This is a hot load at 3,210 and should be worked up to.
Andy, did not mean to run off with your thread, what this all boils down to is that the 260 is an excellent cartridge for just about any application from deer size to varmint size critters. Buy a good rifle up front. with a 1-8 twist, if you can find the twist, and your son will have a lifetime companion.
Ed