His test data was from a reloading manual, He mentioned which one but I don't have the article here to check. He used the load that produced the most velocity/bullet type and weight. As much as possible bullets were same type, ie. Nosler Ballistic tip etc.
His only "published" data were at 200yds and it was ft/lbs of energy and the final number was from some formula that he called the "L" factor. He quoted where the formula came from, but the same formula was used on all loads.
It was just a straight comparison of ft/lbs of energy remaining at 200yds per grain of powder used.
In the sub 30cal category, the 7-08 was most effeceint and the over 30ca it was the 35 cal. with the 35 Whelen AI number 1 and the standard Whelen as number 2. I think the 350 Rem mag was 3, but not sure. All of them beat out the 30 cals.
This doesn't mean they produced more energy than the other rounds, it was more energy "for powder burned". This was an efeciency test, not an overall power test. A 300 Win Mag still had a considerable amount more energy, but there was a price to pay, more recoil, more muzzle blast and more costly in terms of powder used.
The only ones that beat out the 35's were the big boys like the 458's (not the 45-70, it wasn't listed) and 416's. The article is a good read.