FWIW, the military style sling on that particular rifle was put on backwards. The end that comprises the shooting loop, which can be adjusted to the individual to use as a shooting aid, should be on the front swivel. The tail piece, which adjusts the length of the sling for carrying, goes on the rear swivel. A properly installed military style sling will not mar the stock finish. A classic shooting sling for a '57 M70 might be a Whelan sling,or possibly a Brownell's Qwik-Set Latigo. Both have front loops that can be adjusted for size for use as a shooting sling. A nylon version of the Brownell's is the Outdoor Connections "Super Sling", or at least it used to be.
backtobethel, looking forward to nice pics of your rifle!
