I think you got the comma in the wrong place.
It should be about 3,500 to3,700 fps
I loaded some 30-30 and 308 with 55 gr. bullets and imr 3031
For some reason they hit higher than the 150 gr loads.
Accuracy is not there because only the plastic of the sabot touches the rifling.
Less recoil and fun to shoot.
Never thought about loading 7.62x39 may have to give that a try with some of the
62 gr green tip bullets I picked up.
Thanks for the reminder