[jmr40]

That is why 38 Super and 357 mag was invented. Cops found that neither 45 nor 38 specials would penetrate car bodies during the gangster days of the 1920's and 30's. The 38/44, 38 Super, and later 357 mag were invented to solve that problem.

That is also the same reason 45 was never seriously considered by the military after WW-2. They found during the war that 9mm did a much better job of defeating barriers and was not a handicap at all compared to 45. The military tested 9mm vs 45 in 1946 and wanted to upgrade then. They found that 45 would bounce off a GI helmet, but 9mm would still penetrate helmets at ranges exceeding 100 yards. But budget cuts and warehouses full of 1911's meant the project was shelved until 1985.