Just a comparative post at max velocities as found in the load data from 4 powder brands. These numbers are for a 180 grain bullet and rounded to the nearest 10 fps. tossing in the .308 Win and .30-06 for comparison.
To be fair, I omitted the data from one powder in particular, which puts the full-length cartridges well out of reach of the short mags. But there wasn't data listed for ALL of them so I tossed the high numbers out.
Comes from the short neck on the.300 Win casing. There's only about 1 grain H2O difference case capacity between the two. But when getting into the heavier (read longer) bullets, the bullet base begins to extend below the bottom of the .300 Win case neck and intrude into the space where powder could be. It would be even more pronounced with a 200 grain bullet and is the reason you never see .300 Win 220 grain ammo.
As far as I know, these are all instrumental velocities from 24" test barrels. So real life velocities for the RCM and short mags will likely be lower than shown and velocities from the others which may be 26" - 28" barrels will likely be higher.
Actual chronograhed data from 180 gr Hornady factory ammo out of the 20" barreled Ruger runs 2800-2850 fps. Far below the instrumental test velocity.
Remember energy is NOT proportional to increase in velocity...just because one is a hundred feet faster or slower doesn't mean it hits with one hundred more foot pounds of energy.. Old Strutt needs to put the energy difference chart up, you'll really be shocked if he does !!!I'll bet that we a at 3500 is almost twice the good ole .308 win, even though it's approx 900 fps faster !!