I had a National Ordnance 03A3, serial number 5,001,680 .
It was one of the first rifles I ever purchased. I had read "Bolt Action Rifles by Frank De Haas", and his nice little quote of these receivers being given a "clean bill of health".
What an irresponsible load of CCCC. Shill gunwriters just won't call a spade a spade for fear of upsetting someone important.
The headspace on my National Ordnance increased as the rifle was fired. It became more and more difficult to open the bolt, as the bolt peened its way into the receiver.
I traded the rifle away. Today I would strip it for the GI parts.
An interesting read on the history or National Ordnance.
The granular finish on the carbine receivers is similar to the A3 I owned.
National Ordnance M1 Carbine
If you shoot enough, you will learn that you need to wear shooting glasses. I have had two out of battery slamfires in Garands. In the first slamfire, my glasses were pitted from brass particles. Later I put on the glasses and aimed a Garand at a mirror. From the pit, I was able to determine that one brass particle would have gone straight down my pupil. The second slamfire, the blown off rear section of the receiver shattered my glasses. Still, no brass particles got in my eyes.
I also have had pierced primers in M70's. That action blows hot gas directly down the firing pin shaft and into your eye. Glasses protected me again.
If you notice, David Tubb is always wearing shooting glasses. I have no doubt he learned the hard way.