That could account for many older cartridges having a traditional muzzle velocity of 2200 ft./sec.
.33 WCF, .30-30 (170gr.), .30-40 (220gr.), well, maybe Winchester cartridges...
Interesting thread, though.
I know, to calculate energy based on speed and weight, all you do is square the velocity (ft/sec.) divide by a constant (450240) then multiply by weight (grains) and what you end up with is energy expressed in ft./lbs.
So, let's take one of the above mentioned cartridges...the .30-30.
When loaded with 170 gr. bullet, muzzle velocity is 2200 ft./sec.
So here's how the formula would go....
2200 x 2200 = 4840000
4840000 / 450240 = 10.7498223169865
10.7498223169865 x 170 = 1827.469793887704
...or, a little over 1827 ft.lbs. ME
Learned that from a Wiley Clapp article.
"Stopping Power" obviously involves a little more than just pure energy, but that is how part of the equation goes, anyway.
Maybe we should look at "Stopping Power" as the bullet's ability to transfer the available energy to your quarry.