I do have serious doubts that patterns are going to be improved by roughing up the choke. As to slowing the wads though it must be understood this is a "Relative" term. This can be well understood as a slowing of the rate of acceleration. The shot itself would not be so much affected by the roughness as the wads, thus would retain their velocity. "If" we were speaking of roughness all the way down the length of the bore then yes, if it slowed the wads it would slow the shot as well. If however you slow the rate of acceleration of the wads in only the last 1"-1˝" you will not affect the velocity of the shot by much. To prove this either way would take some very extensive testing, including high speed photography of the shot exiting the muzzle to see for certain if this roughness did indeed prevent the wads from disrupting the base of the shot charge. This would it would seem to me to be mostly a moot point with plastic wads with shot cups anyway.
