[GingisK]

A pellet has a cone-shaped tail which seals the barrel's clearance with the pellet. That airtight fit, even in rifled barrels, makes much better use of the air pressure. Air escapes around a BB, losing acceleration. I suppose the only way to know for sure is to make measurement with chronograph.

Your equation is rather messed up:

F = m * a; a = F / m (acceleration)
V = a * t; V = F/m * t

I have had BBs guns and pellet rifles. The pellet rifle had considerably more destructive/penetration power. On the other hand, I've never owned a BB gun that could be pumped up like a pellet rifle. I have owned CO2 versions of each; and, pellets always seemed more effective to me.

I searched the Internet for air rifle ballistics. Detailed information seems to be available only for pellets. Maybe BBs are not considered worth the effort of making the measurements, perhaps due to their inherent lack of accuracy.

[bert]

My Crossman air rifle will fire both pellets and BB’s.

As a practical matter, I shoot only stray cats that hunt birds at my feeders and squirrels that get out of hand. I shoot BB’s at what I think of as half power. The intent is to discourage rather than harm or kill.

However, the info you provided will be useful should the need arise. When pumped ten times the range and accuracy are quite effective.