The lighter bullet is moving faster out of the barrel, and produces a little more energy. The normal rule of thumb, is the heavier weight bullet will produce more felt recoil, than a lighter weight bullet (laws of physics). That is under the assumption that all else remains the same, just a bullet weight swap. The difference in felt recoil should be very minimal between 165 grain to 180 grain weights. With low cost practice ammo, you don't usually get many choices in bullet weights, and I doubt you could tell the difference in felt recoil. Normal factory 40 practice ammunition specs around 1000 fps and 400 ft lbs of energy. If you check around, I think I have seen some 40 practice ammo in the 350 to 370 ft lbs energy range, which should produce less felt recoil.
I use CorBon for all my SD ammunition. In 40 S&W with a 135 gr JHP bullet, it produces 1325 fps and 526 ft lbs of energy. As the CorBon bullet weights go up, the foot pounds of energy and speed goes down. You can really feel the difference in felt recoil, using this ammunition, versus standard practice ammo. I also use CorBon +P 9mm 115gr JHP, which has 1350 fps and 466 ft lbs energy, and also Corbon +P 45acp 165 gr JHP, which has1250 fps and 573 ft pounds energy.
Bob
