I shot some in my 260 using the 123 Lapuas. In my one 260 it shot in the .3s to .4s and was a hotter load than my H4350 load which was cronographed @ 2975fps. I didn't get a chance to cronograph the RL17 so I can't say for sure what the actual numbers are but would guess them to be 3000fps+ with the load I shot.
My new 260 did not like the RL17 load I shot in my old rifle. So its back to the drawing board. But then its the pickest damn rifle I have had in a long time esp for a 260. It only likes an shoots one load and thats with Varget.
A bud tried it in his 260 and it didn't work. I tried it in my 6.5x47 and it didn't work, but it worked well with others like 6xc, etc. for friends who tried it. For me, 100 yd groups were awesome, but 500 yds went to hell.