Thanks for these figures, Mat! The .40's recoil, while shooting my P229R duty pistol, is starting to really hurt my aging, ailing, formerly "strong" hand*. I was considering going back to a G22, to get a lower bore axis, and the cushioning effect of the polymer frame, but then my chief just authorized us to start using .45 ACP as an alternative duty pistol cartridge, in the G21, as well as some SIG models and the S&W M&P45. (Our duty cartridge for uniformed personnel had been the .40 since 1997, until last month.)
I had been told that a G21 recoiled less sharply than a G22, but I wanted to find some numbers to verify that. You have just provided the numbers, and I am grateful. I would rather not switch duty pistols in the twilight of my LE career, especially as we buy our own duty firearms, but this may be a long twilight, and even a small bit of relief may be cumulatively significant.
*I am not blaming the .40 for causing my problems; if shooting is a factor, and it probably is, then those .44 and .41 Magnums I fired in the 1980s played the larger part.
Rexster, I'm glad you found my numbers helpful. If you don't mind, I'll offer a few more to help put them in perspective for you. I'm not all that familiar with the Sig lineup, and am not really sure what the R model is, so I crunched the numbers for a standard P229. It weighs, with its alloy frame, 39.6 oz, loaded. With the same generic .40 cal load from the other post, 180 @ 1050, that gives, 5.61 ft/lbs of recoil at 12.09 fps. That means that while a G21 does indeed recoil about 5% less than a G22, it actually kicks about 8% harder than the standard P229.
As for the low bore axis, while that does reduce muzzle flip for a given amount of recoil, it does so by directing it into, instead of over, your hands. Less motion but more shock, if you will. Not knowing your hands, I don't know which you'd prefer to avoid.
Another consideration you mentioned was the cushioning effect of a polymer frame. In physical terms, that doesn't alter the total amount of force that gets transferred to your hands, but it does spread the impulse out in time slightly, thus lessening the peak force. I don't really know how to put a number on that effect, but I don't think it would come anywhere close to making up for the higher total energy.
Another factor is the size of the grip. A fatter grip would spread the force over a wider area, thus reducing the force at any one point, much like the snowshoe effect. Grips don't really come much fatter than a G21. I suspect that would have more effect than the flexing of the frame, but I still don't think it's enough to make up for the higher total.
For a real, significant reduction in recoil, your two best bets are to use either a lighter load in the same gun, or the same load in a heavier gun.
For example, Federal makes a reduced recoil loading for the .40 S&W, with a 135 grain bullet @ 1200 fps. That's a much lighter bullet going a little faster. Fired from a standard P229, that gives 4.24 ft/lbs of recoil, at 10.53 fps. That's a whopping 24% less than the genetic load I've been figuring with so far.
The two flies in that ointment, of course, are whether or not your chief would permit you to use less powerful ammunition, and whether said ammunition would be as effective, if you ever needed it.
The other option is a heavier gun. I noticed, as I was digging for specs, that Sig also makes a P229 with a stainless steel, instead of aluminum alloy, frame. That version weighs 49.6 oz loaded, and thus cuts the recoil of the standard load to 4.47 ft/lbs, at 9.63 fps, or a 20% reduction over the standard P229. That'd let you keep the same gear, manual of arms and training, too.
If you really wanted all the reduction get, you could use the light load in the heavy gun. That would get you down to 3.39 ft/lbs, at 8.39 fps, about 40% less than the standard setup.
