Maybe I missed it, but I don't recall anyone saying "that they shouldn't be moving until the ejecta comes out of the barrel". "IF" they did they were wrong, recoil starts the instant the "Ejecta" starts to move. However, just for the fun of it lets assume you fire 1oz of shot, with a 35 grain (.08oz) wad over a 22 gr (.05oz) powder charge & assume the base of the wad has exactly 27" to move to the muzzle. Assume this fired from a 7lb (112oz) gun. Just as the base of the wad comes flush with the muzzle the powder gases will have filled the bore. While not absolutely correct it will be close enough for this scenario to take that half it's weight has moved the 27" length. Thus 1oz +.08oz +.025oz = 1.105oz. (1.105 x 27) ÷ 112 = .266. Thus at the instant the wad clears the muzzle the gun will have, in free recoil, moved .266". The rest of it's movement will be from the result of accumulated inertia. Now assume a standard target load velocity of 1200 fps. Even if there had been a totally uniform acceleration giving an average bbl velocity of 600 fps the charge would have traversed that 27" in .00375 sec. As acceleration is of course much more rapid nearer the chamber let's assume an average of 75% of acquired velocity or 900 fps It would then have a bbl time of .0025 sec. I have no doubt a change in acceleration rate of this magnitude would be readily felt, even though measured recoil would be identical for both. However this is a change in acceleration rate in excess of 30%. I have grave doubts that as long as the load was always adjusted to give this identical 1200 fps velocity, that any change one could make to internal bore dimensions or changes in powder burn rates, while maintaining a satisfactory load whould ever, & being extremely liberal, amount to a change as large as 5% in actual bbl time.
So small a change will require much thought & planning to even test & be certain that other external factors are not playing a more important role in what's "Felt" than an actual change in the recoil itself.

Last edited by 2-piper; 09/04/08 03:35 PM.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra