My 1972 44 mag carbine was due for a cleaning. I noticed that the gas block had an extra hole on its under surface in front of the sloping clean-out hole. It is threaded and empty. I do not have an exploded view of the 1972 model, but other models show no such hole. What's up with that? It would appear to be for a grub screw to lock the front plug, but it already has the roll pins for that. I wonder if this is leaking gas. No, I wonder how much it is leaking gas.