Yes.

For those not familiar, the driving force {no pun intended...} of the process is to increase the strength of a barrel by an explosive loading {other methods are used as well}. In the practical world of artillery and tank guns, one goal is to maximise the strength of the lightest possible barrel. This was why I was wondering if OSR had been researched by ordnance engineers, since it seems logical that very thin tubes have been experimented with.

In a rifle barrel, I am not sure what stress is required {pressure} to cause the autofrettage {"self hooping"} event. Skennerton cites the increase of .303 military chambers by .001 {IIRC} as a result of proofing and since a slight and predictable increase in inside diameter is a result of autofrettage, possibly this process occurs during the proofing of such barrels? The weird thing is I cannot recall mention of increased dimensions of other calibers as a predictable result of proofing which means nothing since I am no ordnance engineer. I watched a few guns get proofed once at the Musgrave Mauser plant in Bloemfontein, RSA but that's my sum total experience {not counting the "proofing" of my waterpipe/firecrackers & BB's "gun" I made when I was 12...}

Getting back to 400NitroExpresses .400/.408 barrel, another experiment comes to mind;

Fire a mild steel, machined solid bullet of .407 diameter thru said test barrel. Obviously this would demand extreme safety measures but it might shed some light on the possibility of reproducing OSR in a controlled environment...

As for the degree, I hope you can ask him yourself.