Re: 260 Rem barrel length?
Wellll, if you can't figure it out, and you don't want to do your homework, just get an '06 and factory ammo and live with the results you get.
If you do want to figure it out, the NRA book, "Handloading" by William Davis is an excellent starting reference.
At less than 10 bucks, this is a lot cheaper than one box of factory rifle loads. The time you invest may be more costly, depending on your intelligence and thirst for knowledge.