Well he could be in his late 50's and I don't see why some one even in their 70 could not want to take up hunting at such and age.
US pulled out of Viet Nam in 1975 figure a minium enlistment age of 17 gets you 58 years old.
Regardless he bought a rifle and will probably have to take a hunters safety course since he is over the grandfather age for most states.
He is also saying at 6'3" and 250 pounds the US Army felt he was a ideal candidate to carry a M60.

Al