Becomes less powerful at a slower rate.... :)
The tubular magazine is the weak spot of the lever action. Round or flat nosed bullets shed velocity faster than pointy ones.
Or You can only use the lever action 30-30 as a single shot with pointed projectiles. Or a two shot One in the chamber one in the tube;-)
The bottom line for those of you who think the 7.62x39 is to weak a cartridge. I think you have 6 people here who may disagree with you. Plus many more in the armed forces.