Several years ago I took sample pieces that I had completed to a close friend who does military aircraft testing ....the parts were tested and showed 1.2-1.5 mm surface depth hardening and I was informed that all had passed mil spec. S-6090A which is the military aircraft spec for low carbon steel hardening.......and that is good enough for me.........
I have also hardened some aircraft parts over the years and these parts require testing and certification before return to service (paper trail from a certified testing lab).....color is not on the list of importance....depth and quality is.......these parts are magnafluxed and red dye tested as well, before certification showing any imperfections.......
Miller-
I would guess you read ALL the previous posts, not sure......?...
If a metal lab inspects my parts and says the hardness depth averages 1.2 to 1.5 mm, then I believe their findings to be correct and valid, their x-ray and micron microscopes are quite accurate I think, since they inspect for hidden voids, blisters, structural integrity and the like, not only surface variation and hardness......and since all the parts pass mil spec S 6090A at the temperatures that I am using there is no further information that I require......
all the parts are approved for return to service, guns included, as per the lab......I don't know of any gunsmiths that use a lab for CCH, do you....?....I use it because it is owned by a close friend......
Since you appear interested in some more data, I suggest you take two Flues receivers that you mentioned, case one and run destructive tests on both receivers. You would need to crush both receivers in a press with meters and gauges attached. This would give you the 'structural' comparison testing you seek........A against B.....both from the same manufacturer, same alloy, same size etc......Or you could load both weapons to extremes with gradual increases until they explode and measure the results....Or you could just saw them in half and study the loop.......
Since you have NO clue what temperatures I am using, you therefore have no way to reference this information against your machine shop handbook and your charts and graphs........and since you have "never cased" one single part yourself, I don't think you understand what is involved....maybe as an observer....?.....Maybe your machine shop did not have a high tech aircraft metal lab.....?......Maybe you should read some books on aircraft inspection parameters first, then read your machine shop book.....?.........
