When we're messing with these old scopes, IMO the problem is not the filling but rather the sealing. The older Weavers, in addition to having no internal lock rings preventing easy disassembly, also had parallax adjustment instructions involving loosening and moving the adjustment turret base and thus releasing any gas inside. In order to retain the nitrogen, first it's necessary to adjust the parallax if needed and reseal the turret base; then and only then can the scope be purged, filled and reassembled. The mainmost sealer with these older Weavers, as with all older scopes, is the grease applied to the threads and sealing surfaces prior to reassembly.
Regards, Joe
