The heel of the receiver should sit flat on the stock, yours was obviously sitting above the the stock, as you have a small pillar of bedding material where the heel sits.
It is my opinion that the heel should be completely resting on material, no gaps under it, and for safety reasons, there should be a gap forward of it.
Inspection of like new Garands (I never got to handle new M14's) consistently reveals this air gap forward of the heel under the receiver. It has to be a deliberate design feature of the Garand action. It is my opinion this air gap is a gas vent in case something really bad happens. Gas will go down the magazine, gas will vent out the sides through the left and right air gaps, but gas will not reach the shooters face as long as the heel is tightly fitted to the stock, or as in the pictures above, a layer of two part epoxy.
I have seen actions bedded so deeply in the stock as to bury that air gap in epoxy, and I think that is a mistake.
As a result, the rear lug was taking a majority of the recoil load, which overloaded the thinner sections of the stock.
Conjecture. In a military stock, the rear tangs distribute the load in the stock
I am certain the rear lug will also carry recoil load, and maybe it was supposed to do that. I assume it was to make the whole receiver stock fit more rigid, keep the receiver from twisting. I could not tell much of a difference in accuracy between a non real lug receiver and a rear lugged receiver. The gunsmith who lugged my Garand said a lugged receiver would hold its bedding longer.
In so far as claiming the rear lug carries more load than the tang, which implies stressing of the action, I don't see how that is possible based on how actions are bedded. All the routing of wood is done at the same time, and then the epoxy is poured in all recesses, and the action squeezed on top. At that moment the epoxy has the consistency of peanut butter to melted butter, depending on the epoxy. There will be no stressing of the action due to the epoxy. The action must go in stress free or there will be gaps in the epoxy. Once the epoxy is cured, there will be deliberate downward tension on the front of the action, back on the tang, due to the barrel being pulled downward at the upper ferrule. This is intentional. This bedding was figured out by the early 1960's, might be about five pounds of tension on the barrel at the upper ferrule. Almost all of the why's and wherefores of Garand/M14 bedding was figured out 60 or more years ago, and no one knows what alternate configurations were tried and discarded. Pretty much like the processing of
cassava into something edible, no one knows how it started, we simply copy what was done before. Because it works.
The receiver was not bedded in the stock correctly.
I am not going to try to justify someone else's bedding from a picture. I have seen worse bedding. Pretty bedding is an art.
It is more likely that whom ever removed the action, broke the stock due to the very tight fit of receiver to stock, and getting a M1 or M1a action out of the stock requires the action to move in an arc because the barrel is hooked to the upper ferrule. A previous owner just beat on the buttstock too hard and should have used a rubber mallet and just tapped and tapped to get the action out. It was his misfortune to break the stock instead of the bedding. Bad things happen.
A bud of mine, two tour Special Forces, joined in 1964, he claimed the GI M14 buttstock broke during bayonet practice. The stock broke at the pistol grip during vertical and horizontal butt stroke practice on the dummy. If you notice, on original military M14's, the stock has internal metal bracing in the magazine opening.
Nothing made by man cannot be unmade by man.
