Murder weapon from 40 year old cold case in use by police

[downzero]

And back 40 years ago they could compare ejector marks and firing pin indents.

That's all a bunch of nonsense. Firing pin indents and ejector marks aren't unique to a single firearm.

There seems to be at least some scientific evidence that even rifling marks aren't unique to a single firearm.

Ballistic evidence is more like complicated pseudoscience than legitimate scientific analysis.