I do not quite agree with your analogy. Velocity is directly proportional to pressure. And pressure is basically Volume X Mass(powder). IMO it is harder to regulate larger Volume and larger Mass(powder).

Again IMO it is easy to regulate a small amount of powder. Go to a BP Silhouette shoot. Normally the fellow with the most accurate rifle is normally shooting the smaller charge. With 4 T7 pellets the mass and volume is great. So a variation of pressure is IMO more likely to occur. Again, just my opinion. Tom.