Shear and small bore air cannons

[Technician1002]

I was doing some study on laminar shear of fluids. This is the slowing of a fluid near a stationary wall. There is a speed gradient to the middle of the flow. In large diameter pipe, the center of the flow is not slowed very much by the slow edges of the flow.

I began to think this is another case where a sabot would have a huge advantage as more of the flow is not in close proximity to the wall of the barrel.

Just how much flow restriction in small bore air cannons is there? When the center of the flow is no more than 1/8th inch away from the stationary barrel wall, is this a significant limitation to the maximum speed you can get from airsoft pellets in a lower pressure home made BBMG?