I would like to know if most makers of DR use the above procedure on all their parts during the different stages of manufacture ??

It doesn't make sense to do it on all the parts at all stages of production ! There are various types of nondestructive testing , radiographic, ultrasonic, magnetic particle are the most common.Each has it's drawbacks and benefits.When and what type of inspection will vary with the part and how it's made.

Interesting all the same maybe the metal blanks are done and cert by the mill before shipped out to the buyers/manuf ??

thanks for the reply.

It really only makes sense for barrels of older guns if a gunmaker is offering warranty for them.