There's conflicting data out there. Some folks advise that 1911 pattern pistols are unreliable in 9mm chambering. The point of contention is that the .45 acp design was for a cartridge length 1.275" whereas the 9mm is only 1.169". The OAL difference is said to create random chambering problems in the 9mm caliber.
But some competitive shooters recognize the difference in lengths, but say it's of no import and 1911s in 9mm are as reliable as the larger calibers.
I am confused. Are 1911s equally reliable in both .45 and 9mm? If so what have the manufacturers done to make it so? What are the facts?