The .40/9mm is one reason that I never put more than one caliber on the shooting bench at once. My ammo boxes are clearly marked and no one messes with them but me, but a few months back had my kids and step-kids out at a friends range, introducing them to shooting various calibers. Everything was fine through the .22 stage, they all fired various single and double action revolvers as well as some semi-autos in that caliber. We then went to the 9mm, with a C9 Hi Point and Ruger P95 to shoot. Up next were the two .40's, my JCP Hi Point and SW40VE. In my stepson's haste, he had grabbed a magazine for the JCP and before I cleared the shooting bench, had loaded it up with Federal Champion 9mm. I loaded a magazine with .40 and went through a demonstration, firing ten shots till the slide locked back, then traded places with him. He locked and loaded the magazine that HE had loaded. First shot, BANG... FTE. I had him drop the mag onto the table and pull the slide back, the spent brass fell to the ground. He reloaded and racked another round in, took aim, BANG... FTE.
Now I have almost 1k rounds through this pistol and NEVER had a FTE, so I took it for a closer look. Dropped the mag, locked the slide to the rear, but this time the spent case didn't fall out. I took a dowel out of the shooting kit and knocked it out, picked it up and looked at it... I will say one thing for the Federal brass, it WASN'T split, has one hell of an expansion though! Picked up the first one, was the same, read the stamp on the rear. "9mm"... handed it to him, said see anything wrong with this?
He drilled a hole in the two cases and wears them on his keychain...