Originally Posted by BigUglyMan
I'll be trying another chrony this weekend. That said, I doubt that the particular chrony would have suddenly decided to lie when it was truthful about the 270 I shot before and the 308 I shot after.
Let us know what you figure out. But don't be surprised or too disappointed if you find out your 300 Win Mag is shooting a bit slower than you thought. Doesn't mean it's not a good cartridge out to 900 yds, but if your's will keep pace with the 300 RUM shooting equal weight bullets out of equal length barrels then your 300 WinMag would be a good reason to "never say never". Yet I'm comfortable saying "No Way" in this case. Check out some reloading manuals. None of them will come close to the velocities you claim with those bullet weights.
Set one of your 300 WinMag cartridges next to a 300 RUM. The maximum resultant velocities should be a foregone conclusion. The 300 RUM case is what my 300 WinMag cases would look like if I pushed them to the velocities you're claiming, and I doubt the case heads would still be attached.
I knew this going into my rifle build, and I built the 300 WinMag anyhow, but I needed a carry rifle weighing no more than 9 1/2 lbs completely scoped and outfitted/loaded. I pack in and pack out for most of my hunting.