Sooo..... on the subject of the action screws.
The rear screw has that long-ish shouldered section, but ultimately it has the same length of threads (.375") as the front. Both are 1/4" x 28; the front screw is 1" overall (1.02"). So could one not use the front screw in the rear, as long as you had a tool/bit that it could be reached into the small recess?
Also is there any reason that a fully threaded screw would not also work?
If that's the case, would these work?
https://www.ti64.com/product-p/5135.htm