[TChris]

The .40 S&W is a cut down version of the 10MM. Severely underpowered, not much better than a .38.

I'd have to disagree pretty strongly there. Its essentially the same load as what the FBI was getting in their 10MMs, since the full load had too much recoil for good follow-up shots. They figured out a load that worked really well, then created the 40MM around those numbers. Its not underpowered at all. But, this probably isn't the thread to get into it...

[Dead Corpse]

No. The .40 S&W is what they switched to because the wussies couldn't handle the 10MM. The .40 is the same diameter round, but in a case about the same length as a 9mm. No where near the ballistics of its big brother.

Yer talking a .40 with a 180gr at 900fps vs a 10mm 200gr at 1200 fps. No comparisson what so ever.

[Deguello]

"Its essentially the same load as what the FBI was getting in their 10MMs"

The Bren 10 and the S&W 40 are essentially the same for ballistics. The Bren 10 had problems with the longer action. For the fast powders being used, the longer brass was just wasted space. Reloaders know that the small amounts of fast powder in a long case in itself creates problems with the burn and performance.