The article posted by Bis45 stated that the cylinders would be checked by the Magnaflux process.

This process is non-destructive (does not destroy the part being examined) and usually is performed using magnetic particles to reveal an inclusion or crack in the object being tested.

It has been about 35 years since my cursory training on this process, so that’s about all I remember about the process.

Another NDT process is the “dye penetrant” method of revealing minute cracks in metal, but this method would not reveal a void or inclusion in the metal.

Check the yellow pages or do a search on “Non-Destructive Testing” to find someone in your area that may be able to do this for you. Aircraft structural repair facilities often use this process, so that would be another area to check.

Or, you could just shoot and enjoy the gun