Attached is an Adobe file about the Chu Lai Sniper School and, other than a few CIA test rifles, the snipers routinely used the M21 and Lake City M118 SB.
Lones Wigger is easy to find on the internet and we exchanged emails once about RVN records.
http://www.sports-reference.com/olym...-wigger-1.html
http://www.facebook.com/people/Lones-Wigger/1537531224
Virgil Umphenour runs a guide service with his son and daughter in Alaska
http://www.huntalaskawithus.com/about_huntalaska.htm
One day in RVN, Virgil sent word that he was going to court martial a "raggedy ass, wet behind the ears lieutenant" if I did quit being an asshole.
I had tactical control of the snipers in the field but he had administrative control.
I would just say that my experience was about as the adobe file says. Lots of 100 - 500 yards kills and wounded and only very, very seldom are you in a situation to get a really good extreme range shot.
I believe the Iraq record with the 308 was set at 1250 meters with a M24 bolt gun using the M118LR (not M118 SB) with the 175 SMK and is borderline super sonic range but I don't know the atmospheric conditions so I would not make any definitive statement about it other than a good shot is a good shot.