Mathematically, there's a significant difference between the calibers. According to Wikipedia, 9mm Luger has the following muzzle energy:
According to Wikipedia, .40 S&W has the following muzzle energy:
It is a bit difficult to always compare apples to apples here. But if we compare a 124 grain 9mm Luger Federal FMJ to the 165 grain .40 S&W Federal FMJ, that's 364 ft-lbf versus 468 ft-lbf respectively.
(468 - 364) / ((364 + 468) / 2) = 0.25 or 25%
That makes sense to me because with a .40 S&W you're simply pushing a heavier bullet with more powder than a 9mm Luger.
Of course, now you can get into heavier gun versus lighter gun, longer barrel versus shorter barrel, perhaps even revolver versus semi-auto. All of those considerations will affect felt recoil.
| 7.45 g (115 gr) Federal FMJ | 1,180 ft/s (360 m/s) | 355 ft⋅lbf (481 J) |
| 8.04 g (124 gr) Federal FMJ | 1,150 ft/s (350 m/s) | 364 ft⋅lbf (494 J) |
| 8.04 g (124 gr) Norma ENVY FMJ | 1,345 ft/s (410 m/s) | 498 ft⋅lbf (675 J) |
| 7.45 g (115 gr) Underwood JHP +P+ | 1,400 ft/s (430 m/s) | 501 ft⋅lbf (679 J) |
| 3.9 g (60 gr) RBCD TFSP | 2,010 ft/s (610 m/s) | 538 ft⋅lbf (729 J) |
According to Wikipedia, .40 S&W has the following muzzle energy:
| 10.69 g (165 gr) Federal FMJ | 1,130 ft/s (340 m/s) | 468 ft⋅lbf (635 J) |
| 7.45 g (115 gr) Cor-Bon Glaser | 1,400 ft/s (430 m/s) | 500 ft⋅lbf (680 J) |
| 10.04 g (155 gr) Federal HST | 1,160 ft/s (350 m/s) | 463 ft⋅lbf (628 J) |
| 8.74 g (135 gr) Underwood JHP | 1,400 ft/s (430 m/s) | 588 ft⋅lbf (797 J) |
| 12.95 g (200 gr) Doubletap FMJ FP | 1,050 ft/s (320 m/s) | 490 ft⋅lbf (660 J) |
It is a bit difficult to always compare apples to apples here. But if we compare a 124 grain 9mm Luger Federal FMJ to the 165 grain .40 S&W Federal FMJ, that's 364 ft-lbf versus 468 ft-lbf respectively.
(468 - 364) / ((364 + 468) / 2) = 0.25 or 25%
That makes sense to me because with a .40 S&W you're simply pushing a heavier bullet with more powder than a 9mm Luger.
Of course, now you can get into heavier gun versus lighter gun, longer barrel versus shorter barrel, perhaps even revolver versus semi-auto. All of those considerations will affect felt recoil.
