All these posts indicating there is no difference between 9MM and .40 S&W are obviously written by people that have not used both. One simple test will show the difference. Line up 4 or 5 1 gal. milk bottles filled with water. The .40 S&W slug (Win Ranger) will end up in the fourth bottle when fired from 5 ft. The 9MM will be lucky to get out of the first bottle. You will also find the .40 Expands to a significantly larger size.
The 9 is certainly cheaper to shoot and the .40 will hit every bit as hard as a .45
I have tested about 20 different 9mm loads with milk jugs. And I have tested about 10 different .40 loads with milk jugs. I usually set up 15 jugs at a time. 3 wide by 5 deep. Then shoot down the middle row.
12 of the 20 9mm loads ended up in the 3rd jug.
8 of the 20 9mm loads ended up in the 4th jug.
3 of the 10 .40 loads ended up in the 3rd jug.
7 of the 10 .40 loads ended up in the 4th jug.
What 9mm load did you test that didn't make it out of the 1st jug??? What gun was it shot from???
I did not find the .40 to expand "significantly" larger than 9mm. I would say on average the .40 loads that I tested expanded to about 0.090" more than the 9mm loads.
I have since found a much better testing medium-wetpack. And my results with the wetpack reflect my results with water jugs.
This being said, I think the .40 does have a slight edge over 9mm regarding terminal ballistics.
But I don't feel undergunned at all with my little 9mm pistols!
Here are a couple links to my recent wetpack tests: