In Porco Rosso, why does he inspect every round?

Question

In Porco Rosso, Porco can be seen inspecting every round that he just purchased. He discards some and keeps others.

I would assume these are left over from WW1, and as a result they are a bit old and potentially no longer good. Perhaps he is checking to see if the bullet is pushed in, if there's any cracks or rust, perhaps they are just low quality.

Answer 1

He is likely checking ammunition for oil or grease. Oil or grease on the cartridges can produce excessive chamber pressure leading to personal injury or death and/or damage to parts of the gun.