One point of order, while 4140HT is pretty strong, it may not have the same properties as an action heat treated to the ideal hardness. I have tested a few rem 700 actions I had when I had access to a rockwell hardness tester and 36-38 sounds like about what I got. So if you duplicated a rem 700 from 4140HT which is 28-32 rockwell C it would not have the same properties as the action you copied, it might still be plenty strong though.
Note the difference in hardness between the two parts of the action, that is on purpose too, running the same metal at the same hardness together will wear more than if one part is harder than the other.
I have also seen a lot of 4140HT parts that were scrapped due to cracks in the bar stock, some of them BIG parts 24" in diameter and 24" long....cracks found after about 30 hours of machine work
. Gunsmith friend made up some 1911 compensators from 4140HT and after he had them finished and blued he saw the crack that probably ran through the whole bar of material.
Just a few things to be wary of....those things are not material specific....for something you are going to put a LOT of time into, buying an aerospace grade of material with certifications might be worth some extra cost.
Bill