The case, as mentioned, is very thin and contributes little, if anything useful, to deflection strength.
DDA
Well, as I try to remember where I got that information, the skin aluminum on a monocoque fuselage is very thin in relation to the cross section of the fuselage but adds tremendous resistance to both torquing and bending of the fuselage. I remember when I read the article that that was the conclusion that I came to. And apparently the low carbon frame doesn't need much stiffening as the Winchester 21 action steel is only about double strength of the low carbon steel but doesn't require case hardening.
I wonder what the difference in hardness is between the 21 steel and unhardened low carbon steel? I bring this up because of the contention that receivers are case hardened primarily to resist wear, say between the knuckle and the iron, which of course should be lubricated and have no wear.
