These are the rounds that Newton designed. I have no data on the 33 Newton and 40 Newton. I do not believe either of them were commercially loaded, but could be wrong.

.22 Newton, bullet 70 grains, velocity 3,250 fps
.256 Newton, bullet 120 grains, velocity 2,980 fps
.30 Newton, bullet 150 grains, velocity 3,175 fps
.33 no data
.35 Newton, bullet 200 grains, velocity 3,030 fps
.40 no data

The .35 Newton had a muzzle energy of 4,100 ft/lbs. The .375 HH is the legal minimum in many countries for elephant. The .375 H&H as currently loaded by Remington with a 300 grain bullet has 4,262 ft/lbs. All data from "Cartridges of the World".

Pete

http://www.damascus-barrels.com/Movie.html