Well, if you need to do some shootin' the M14is sure the one to do it. The carbines being cut down isn't unusual, you even saw examples of them captured from the NVA and Cong. The Bowie looks like a Western example of the Raider bowie. The original Collins model was basically a cut down machete with rather thin stock for a proper bowie knife. During WW2 Western, Kinsfolk & Case made versions. Don't know much about the Case or Kinsfolk versions, but the later Western W49 had the proper blade thickness & became a bit of a classic blade, having been popular with soldiers in Vietnam & produced until Western went under. I'm not sure how many manufacturers there were.
Here's some more info... WWll V-44 Kinfolks Fighting USMC Pilot Survival Knife - EDGED WEAPONS - U.S. Militaria Forum