Some barrels made by other took 03 barrel and machined the chamber area OD, to take an adaptor for fitting the M1 Receiver.
{Some time threaded, sometimes silver-soldered}
If I should die before I wake...great,a little more sleep.
Why do you think they would land @ LAX?
They are supposed to be "intelligent life".
There are no aliens, if there were, we would have sent them foreign aid by now.
When there were no surplus barrels for the M1 Rifles, the people putting the demilled M1 Rifles back together drilled out the M1 barrel, and turned down the 03-A3 barrel to fit in the receiver stub. Dead giveaway is always the remnants of the front sight cut in the 03-A3 barrel.