Are there any reasonably priced scopes that will hold zero while firing full auto on an M14? From prone, with bi-pod; I can maintain sight of crosshairs and target and can fire quite accurate 6 to 8 rd. bursts. Problem is, after about 2 mags. the scope is way out of adjustment. WELL aimed semi shots hit about 1 1/2 FEET to the right! I've tried two scopes (both bottom end price level) a Tasco and a Bushnell, both 4x with same results. Firing regular semi auto aimed shots doesn't effect zero at all. Scope mount is military type with single bolt and rail to fit on left of rec. Everything seems to remain tight, no looseness in mount, rings, or scope. Is full auto just shaking these scopes out of zero and are scopes available to hold zero under full auto?