[Parley Baer]

In my opinion the roots of the .40MM go back to the early 1880's and the .38-40WCF cartridge. Balistics are virtually identical with the same size bore and bullet weight. Parley

[yarddog]

I think you are right about the 38-40. It was a good rifle cartridge but the bottleneck never did work well in revolvers.

[jim_trent]

Actually, the 38WCF (38-40) is a dead ringer ballistically for the .40S&W in equal bullet weights. The 10mm is more powerful than both.

There is no problem with the 38-40 in revolvers. I have three of them. I also have a Uberti/Winchester 38-40 rifle. No problems there either. The 38-40 is much more accurate than the 44-40 (I have several of them too), especially the RUGER Vaquero 44-40 (Baa, humbug). Will provide more info if anyone is interested.