So, if the pellets need to speed up to get out of the way of the following pellets when there are no more following pellets that need would disappear.

The last portion, say the length of the conical section or even close to the diameter of the bore, could as easily fill the space behind with the effect that a considerable fraction of the payload does not accelerate at all or even is slowed. Given the force needed to displace the pellets ahead vs the pressure required to resist the wad, this seems quite plausible. We are still accelerating about 20 feet per second per inch here, so inertia is not on the side of going faster.

There is also the conservation of energy bugaboo. An extra 50 fps for the entire shot charge seems unreasonable. This energy has to be extracted from the expanding gas, at a rate of V squared.

I can't reconcile the observed length of the full choke shot charge with equal acceleration of all pellets through the choke.


"The price of good shotgunnery is constant practice" - Fred Kimble