You probably looked at Eastons website by now, but I should be able to get you close. According to my program, not knowing if your using vanes or feathers, your XX78 2613 at 26" with 100 grain tip should be around 500 grains with an 11.26% FOC. I haven't had a chance to fully update the program this year, but it should be close with a fully assembled arrow. I assumed you were using it for hunting? If you get a chance to weight it, let me know if it was close.
South Dakota - Iowa