Long Branch receiver body metallurgy

[Bladerunner]

I have been doing some research as to the metallurgy of No4 receiver bodies. From what I have found, it appears that UK No4. receiver bodies used Steel. B.S.S.5005/401.

I believe this steel is equivalent to the following newer specifications:
BS970/1955: EN36B
BS970/1991: 655M13
AMERICAN SAE: 3415
EUROPEAN STANDARD: EN10277-4

655M13 Technical Guide :: The Metal Professionals - Acton Bright Steel

My question is, does anyone have documentary proof as to the type of steel Long Branch used for their receiver bodies? Was it the same as UK production or was a substitution made for a more readily available case hardening steel such as SAE 8620. SAE 8620 was the steel the Americans used for their Garand receivers.

Cheers,

Duncan

Information

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[Peter Laidler]

Same spec across the board BUT as allowed within the window of permissable metallurgical mix

[Surpmil]

If you want to investigate further I think I know where there are a number of stripped receivers of various dates that are junk due to the bolt head guide rail being torn out around the release slot.

I believe an X-ray spectrometer would yield the most interesting results. Sins and omissions of long ago might be revealed!