Welcome to the forum.
When was great Grandfather born? Not sure how old you are but it seems like your great Grandfather would have been too old to own a gun made in the 40's unless my math is off. Seems more likely that it would have been your Grandfathers gun. In that case, it might still be possible to still get facts about him from other living family members.
One of the sad things today is that families don't seem to keep information on the lives of their ancestors. Back in the day, there was the family bible where all of the names, birth dates and dates of death were recorded. Today, for most folks, it is Ancestry dot com or nothing.
