Didn't P.O. Ackley write about rapping the action rails of an '03 with a screwdriver handle and having the rails break?
There was an article in 'Rifle' magazine where that was the 'test' of several L/N recv'rs and how they broke. 1980's article I think,,can't recall the author.
Seems there was a separate article in the same issue, a followup of sorts on the 1917 US Enfield and how they could be brittle and break as well. I seem to remember the use of a railroad track as the bang-em anvil.
The recv'r ring crack from bbl removal(?) on them was also mentioned IIRC
The article is one of the more often noted ones in the constant back and forth over wether the L/N '03s are hand held fragmentation bombs or not.
Like the use of damascus bbls w/modern smokeless powders (or any powders at all maybe),,it's one argument that'll never be totally settled to the satisfaction of all.
I have & shoot a Sedgley Sporter.
FWIW, the recv'r isn't glass hard, it will cut w/a sharp file. Probably 're-heat treated' by Sedgley on a stove burner or some such arrangement. Nice rifle.