I don't think it's acceptable that any of them FTF but it seems to be the norm with .22LR ammo. I don't think I've ever taken out a .22 and not had at least a few rounds that didn't fire.

As a kid, our father would give us one or two 50 round boxes at the range to shoot and that was it. We would keep recycling the dud's until they eventually would go off. After we shot up all our ammo, we would start digging thru the piles of spent shells on the ground looking for more dud's. Kept us out of trouble.