I haven't compared 209 primers of different makes however I did find a noticable difference in velocity using a 209 Winchester vs a .25ACP conversion with small rifle primers. I believe the more powerful standard 209 added to the velocity and I have a source that also backs this up. I believe that primers of different power will affect the final velocity so the newer "made for black powder" primers may shoot a little slower than the old standard shotgun 209 primers. Be careful when selecting primers as some of the ones packaged for black powder are just standard shotgun primers repackaged. Some are actually reduced power primers. RWS now makes a specific black powder 209 primer but I cannot find them anywhere.