It sounds to me like the material is approx 30% heavier than a lead bullet. It will have a profile like a 150 grain bullet but weight 180 grains. The drag will match a standard 150 grain bullet.An object in motion stays in motion unless it is acted upon. Given equal drag the heavy bullet will tend to maintain its speed because it takes more drag to slow more mass. Like throwing a whiffle ball vs a baseball at the same speed.