IMR 4064 and Varget w/ 200 Horn SP proved very accurate @ 2850fps in my 338-06 AI. Higher velocities were attainable but this bullet performed best on Mule deer and Elk at this veocity. [will break both shoulders and exit on Elk] Gave rifle to my hunting partner and built 338-08 on 700 SA, 20" #4 barrel 3yrs ago. [ wanted short overall length that did not extend over my head when slung on shoulder] I've never shot factory ammo thru it, Varget and RL-15 work best w/ 180 AccuBond and 200SP Horn bullets. Have reached 2800fps w/ 180's but prefer 200 SP's @ 2600 fps. The 200 SP's at this velocity also break down Elk shoulders and exit. I've taken Elk w/ 358 win, 338 mag, 30-06, 280,7x57, 7-08 all great calibers! 338 cal seems to work best in my hunting envirionment and remains the best performer for what I want it to do.