About 10 yrs ago...I got sucked into the hype on the .40 S&W and jumped in with both feet...
I have a pair of Sig 226's ( one in 9mm, one in .40 S&W ) ....decent guns, but the .40 S&W is a lot snappier recoil and a little more difficult to shoot. My followup shots are just a hair slower with the .40 S&W...
I also have a pair of the small Sig 239's ( one in .40 S&W and one in 9mm ) ...decent guns, but in .40 S&W it takes a lot more concentration to shoot that gun well.../ with some speed and remain tactically accurate.
I had a Wilson combat Protector model, 5", steel gun ...in .40 S&W.../ and I have one in 9mm and .45 acp as well....and of the three guns, the .40 S&W is more difficult to shoot tactically. As a result, I sold the .40 S&W because I wasn't shooting it much...
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As I've gotten older..and some arthritis in my hands too ...I've come to realize a gun in 9mm is plenty -especially with all of the new high quality Defense ammo out there these days..../ its not that I can't shoot the .40 S&W guns I have, I just don't...and when I carry 99% of the time its a 1911 in either a 9mm or .45 acp anyway...
the .40 S&W for me - is an in between caliber...a little snappier to shoot ...and it really doesn't do anything the 9mm or the .45 acp can't do a little better in my view. I keep the guns I have in .40 S&W ...and I reload the caliber...so cost isn't a big deal...but I still only shoot 20 boxes a year in that caliber...( I also have one of the big Sig X-Fives, SAO, all stainless..in .40 S&W ...and when I shoot .40 S&W, it gets 90% of the usage...and its sure not a gun I'd every try and carry at 55 oz..)...its just a caliber that gets left out for me.
A 10mm to me....would be even worse...way more recoil for any given gun in .40 S&W...and I don't see any need at all for a 10mm...