Originally Posted By: james-l
The data I have shows that Rock Island receivers were double heat treated beginning with #285507, nickel steel at #319921. The list shows that Rock Island production did not reach 400000 ??


I've heard this issue addressed before. If I recall correctly
a number of receivers were manufactured and marked at the Rock Island Arsenal but were completed later, I think at the Springfield Armory. Perhaps another member will be along to confirm this.