The Sierra 50th Anniversary Edition lists several powders, but IMR-4350 looks the best to them, with 65.9 grs. as a start with 72.8 grs. listed as max. They say 2800 fps with max out of a Mark V w/26" barrel. Oh, the OAL listed is 3.560" It is right there with the good old standby, the 300 Winchester Magnum!!
I didn't get out to the range today but I will try again as soon as possible. I remember the last time I was using my dad's .300 (not mine) and I belive we were getting half inch groups at 100 yards. I can't remember what bullets we were using though.
Nighthawk, if you go to the Sierra website, they list a number where you can call one of their ballistic consultants who will be happy to give you all the info you need. For example, they gave me great info for using Retumbo powder with 7mm MK's when even Hodgdon could offer no data.