How old was the barrel ?
I suppose a military rifle that gets used more than a few rounds each year for deer hunting can wear out and they can replace the barrel. But I know the .308 rifle that my old man passed down to me is still in great shape and shoots as well as it ever did. It’s about 60 years old.
If it was a Ma Deuce he was probably lobbing bursts of rounds in the general direction. This was not precision long range classic sniper shot...not with a machine gun.
How WORN was the barrel.
I have a 116 year old Krag that has an almost pristine barrel (shoots real good) I have a 136 year old 1873 winchester with a horrible barrel from black powder/mercuric primers and missed cleanings. It shoots ‘ok’.
40 years is in and of itself meaningless.
A Ma Deuce barrel that is not abused will last a long time.