Re: concentric ammo and velocity
I think it could but it would be dang hard to measure without some really technical tools. Since barrels are not bored perfectly in the center of the steel and do have some wobble in them, if your ammo has bad concentricity too, it could change how the bullet enters the bore and other minute aspects of the barrel could indeed change the ES unless you meausured and indexed each round before firing. This is, again, very hard to determine and would require a lot of other variables be eliminated to test it and some of those variables would be difficult if not impossible to eliminate so I'm afraid this theory will remain armchair theory at best. That is why we must make our ammo as close to perfect as possible to try and achieve perfection and cross our fingers we got a good barrel! And there would certainly be other variables in our ammunition that would affect the ES to a much more severe degree.
If it's not far, it's boring.