I've already stated before that the difference in recoil is slight, but appears to be there. Rather than discussing, say .3 foot-pound of recoil, it might be more useful to look at a 10% difference in recoil--which is what Sierra's program calculates is the average difference between the .204 and .223 with 40's.
And with 32's the .204 recoils even less. I mostly shoot 32's in milder winds because they shoots just as flat to 500+ yards but recoil slightly less.
This is why I never could figure out why some people claim there's no difference in the recoil between the rounds. The major factors in cartridge recoil are powder weight, bullet weight and muzzle velocity. Since the powder charges are so similar, the .204 would have to kick a little less, because it generates less velocity with the same bullet weights, and mostly uses lighter bullets. So if a program claims the .204 kicks more, then there's something screwy somewhere. (And it was, in drover's example, because the velocity he used was much slower than the .223 is capable of with 40-grain bullets.)
Whether this makes any difference in an individual shooter's ability to see hits is another question, because that would depend on how firmly they hold a rifle, stock shape, and the field of view of the scope. I normally use somewhat less magnification than many prairie dog shooters for typical shooting ranges, usually around 10x out to around 300-350 yards, and maybe 15x at 400-500.
I'll also state, once again, that in this discussion, average results are more important than individual results. And in the previous thread twice as many people said they could see hits better with .204's as those who said they couldn't. More "samples" (meaning more shooters) tends to average out differences in shooting style, stock shape and scope field-of-view.
All I'm saying is that the .204 has to recoil slightly less than the .223, even when using 40-grain bullets in both rifles, and that slight difference appears to allow a majority of shooters to spot their shots more easily with a .204 than a .223.
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