this is my first visit to this site, so this may have already been discussed....I was visiting a good friend that is a pistol smith (APG)... he was diagnosing a customer's competition pistol that would not eject reliably, even with an 8# recoil spring... he has a range on premise, so the pistol was taken to the firing line, and the ejection port was photographed by a cell phone equipped with slow motion technology for a series of shots....clearly showed the degree to which the slide was not cycling fully... I still use a flip phone, so I thought this was pretty neat and the use of that technology entirely new to me... regards

iPhone 12 Pro is what you seek

High speed flash x-ray would be even better.
There are some nice looking flash x-rays of a 1911 firing floating around.

Good enough to see the barrel link moving during the firing cycle.

The U.S. used high-speed video to diagnose problems with Bofors 40mm guns during WWII.  The Germans used "spark photography" to take high-speed still photographs of weapon components cycling.

The biggest problem is getting flashes when the bullet is in front of the lens.

Did single shots many years ago with very brief flashes from spark generator system.
Precision triggering of the high voltage spark takes a lot of work.