I found this article that has handgun cartridge sales data from 1999.
http://findarticles.com/p/articles/mi_m0BTT/is_143_23/ai_56221596/
According To... Federal Remington
1. 9mm Luger 9mm Luger
2. .40 S&W .45 ACP
3. .45 ACP .40 S&W
4. .38 Special .380 ACP
5. .380 ACP .38 Special
6. .357 Magnum .357 Magnum
7. 10mm Auto .44 Magnum
8. .44 magnum .25 ACP
9. .32 ACP no response[*]
10. .25 ACP no response[*]
* Remington's report of top selling cartridges didn't have anymore handgun loads on the list
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So, I'm looking for data that is more current. The 380 craze is more recent and I think 45 is becoming more popular recently too. Cowboy Action Shooting shooting has also increased a lot in the past 10 years which helps 38special. Also interested to see if 9mm has been dethroned from the #1 spot.
Anybody have any 2011 data?