Maximum chamber pressure for the M1 Carbine?

You wrote proof testing and somehow I read function testing. Thanks for the correction. Guess I score somewhere in the slow normal line for reading comprehension. I attach a screen capture from the History Channel video. It is from the US Guns of WWII episode of the Tales of the Gun series from six or eight years ago. The carbine part is in the last five or six minutes of the hour-long show.

Interestingly, the operator mounted the carbine in the test fixture without a magazine and with the slide stop engaged to open the bolt. Once mounted she inserted the full magazine, released the slide, and blazed away. Nice safety move to avoid swinging a gun with a round chambered all over the place - and repeated thousands of times. The view panel slides on a horizontal track to allow installation and removal while protecting the operator. Unlike the proof testing setup, this one is triggered manually - with the thumb.

I also include the photo of the slide cycling apparatus - again for testing finished carbines. It has five slots, not seven as I recalled.

In another clip three women are doing final assembly of metal into stock. They hooked the receiver into the recoil plate, swung the barrel down, installed the handguard, and tightened the band screw. They did not suspend the barreled action and bang the buttplate to seat the action in the recoil plate. Wonder how these targeted? I have seen another video where the installer does bang the butt on the bench top.