Good Morning John , I don't know the answers to your questions really but ,I had a Pre 64 Model 70 Chambered in the 338 Winchester Caliber ,and when I would take it to the Range where I too were shooting off of a Concrete Table I would lose the sight of the target also ! If you could hold it until after it went off it would shoot better than 1/2" Groups at 100 Yards shooting off of a Led Sled so I assume it was just all about the recoil but I have a couple of buddies who shoot the 300's and they never complained of this ! I bought the Rifle to hunt Bear with but never had the opportunity to fire it in the woods !
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