I have only seen OSR once, and you could barely see it unless you got the light at the right angle - ie the reflection off the barrel.

So yes, I would say a laser or some micro instrument would be needed.

As for "spitting of rifling out the muzzle, ribs falling off",
I have heard of ribs coming away or apart but never "spitting of rifling out the muzzle".

Where has that been written ?