IMR 8208 XBR 123 AMAX IN A Grendel

I didnt have any luck with that powder. Some have... but not me... you will find all the info you want on the 65grendel forum... I ended up shooting reloader 15 with the 123 amax. Shaves the hairs off a gnats face. No other powder shot near as well for me.
 
28.3 and 123 amax seated near mag length with lapua brass hammered in my grendel

Im guessing your barrel is 20" or shorter.. ive been studying this powder for a while now.. my grendel satern barrel was 28" at first i tried this powder no luck.. cut it to 26" coz i wanted to install brake tried this powder again, no luck.. thried with 120 and 123smk 123 amax..did a lot of research and it seems like majority that having good luck on this powder has a short barrel..rl15 gave me a great results too..