Timelinex, if you knew the difference between "caliber" (original definition: bore diameter of barrels in hundredths of an inch but now often stated in thousandths) and "caliper" (a measuring tool such as what's used to measure case length), you would understand my first paragraph. Look 'em up on Wikipedia.
If you want to see something factual that shows the 300 win mag performs better at 1500 yards, go back and read my earlier post; it's factual. Otherwise, contact the US Army Advnaced Marksmanship Unit then ask them to direct you to the folks conducting the tests. If you don't trust me or them, do your own research. Doesn't the absence of the .338's in long range benchrest matches top scoring/grouping cartridges have some credibility? I''m not aware of any .338 that's stayed inside 5 inches at 1000 yards for several shots.
In contrast, I totally agree with you that sometimes/occasionally, one gets a first shot hit at all ranges. It's the odds for/against it I was referring to. Have you ever watched a few dozen of the best long range shots on this planet fire their first shot at 1000 yards on a known range during moderate winds with a good zero and hit within 10 inches of their point of aim? I have and only about 10% of them do on a good day. The higher the wind speeds, the lower the odds are.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master