no idea on the cylinder gap as it may or not make much of a difference in the long run.

there is such a things as guns that are "fast" and some are "slow".

I had a Ruger #1A with a 22 inch barrel and a #1B with a 26 inch barrel in 270 Winchester. the #1A with the shorter barrel was within 30 fps of the 26 inch barrel.

every gun is different. I have chrongraphed several hundred loads of various caliber over an Oehler 33 chronograph and you learn something every time out.

different lots of ammo could be and will probably be different