Some swords were tested, most weren't -- there were just far too many swords, and not enough bodies. They also hired specialists to do the testing, partly to avoid damaging the sword, partly because this sort of task wasn't highly regarded.

It would be funny for a samurai of old to look at all this ammo selection debate. They might have had their precious heirloom sword that was the equivalent of gun people's "safe queen" today. They also had swords they actually fought with -- if they lived during war time. If not, they probably never saw action. These swords got chipped, damaged, and broken fast -- that's just what happens when metal cuts against metal. These battlefield beaters never made it to the museum. In other words, they expected their weapons to break. Here we have the luxury of collecting data about ammo and wondering about "single shot stoppers" and weapon reliability. Back then it was "hack, hack, and hack again," hoping that your sword wouldn't break before you kill the guy.