Originally Posted by what barn door
I am about to ask a question which will no doubt appear silly or obvious to some but here goes anyway.
If pellet xxx is the same weight as pellet yyy, but it has a better (lower) coef of friction/drag then won't that be seen as a higher velocity at the muzzle?...
Theoretically yes, however, all the stated Cd and Ballistic Coefficients that we use are aerodynamic coeffs ie. concerned with the pellet's behaviour in free air. The differences in static and dynamic friction add a further layer of complexity, allied to barrel and air delivery variations between rifles the simple answer is to test rather than try to predict.
Ultimately aerodynamic considerations are relevant to shooting performance, whilst any in barrel variation is likely to be minor and irrelevant the instant the pellet exits IMO.
I've never seen any information regarding a correlation between aerodynamic efficiency and in-barrel loses, there's no reason to think that pellets with high friction/large bearing surfaces should be aerodynamically poor, so it's unlikely to be a straightforward relationship, owing to a different set of variables. [All IMO!].