Dunno, maybe it’s just me but I had to by a Hogue handall to keep mine from jumping around in my hand. I’ve heard muzzle flip can be controlled significantly by just altering your grip and stance but I still think the P99 in .40 has got a little more pop to it than most. It probably won’t make much of a difference at close distances but it still kicks more than a Glock 22.
At the risk of sounding like a wimp, I will say there is a substantial difference in recoil in the 40, compared to a 9. I sold my 40 and bought a 9mm just so that I cound enjoy shooting it. I had a Witness compact in 40 that was all steel and pretty heavy and it was much more pleasing to shoot.
Go rent a .40 at your local range and shoot one first. I had a glock 23 40 cal, almost identical in size to P99. I learned to shoot on a 1911 .45 and I personally can't stand the 40. Every 40 cal gun that I have ever shot, with the exception of Beretta's Cougar, seem to torque/twist in your hand when you shoot them; at least that is my experience and that of several others I have spoken with. I would go with a 9mm myself. The best HP's in 9mm seem to do just as well as most of the 40 and 45 cal HP's out there. And b4 anyone tries to start a caliber argument I said that the best 9mm HP's do as well as "most" of the 40 and 45 hp's out there. The best 40 and 45 cal stuff still performs better, but not by much if you're good with your shootin iron and place your shots where they count. Shot placement is paramount. Get what is comfortable for you to shoot and practice, practice, practice!
I like my p99 9mm titanium so much that I will shortly be buying an all black one to keep it company.
A lot also depends on the ammo you shoot. Different manufacturers use different powders and loads. I can shoot Hydrashocks all day but CorBons hurt my wrist after one magazine.
From hardest to lightest:
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Hey fritz. Have you by any chance tried Hornady's TAP ammo? I've shot it in my sig.380 and love it. I've yet to try it 9mm myself. I currently use the 124gr hydras and am very pleased with how they shoot.