Also, bullets that do go off unconfined, it's hard to tell the difference than the damage and scattering being shot without detonating would do anyway. Plastic shotshells are even worse, they usually just perforate out the side of the plastic hull and go nowhere at all.
The average fps for an unconfined detonation is usually around 300fps, with the case usually doing the flying, since it masses much less than the bullet in most calibers.
I uh also have first hand experience... I crushed a live .22LR by slamming my safe door on it, and it actually hit my leg, it was like an Airsoft hit.
While shooting a primer and actually setting it off might be a million to one event, I can say that small pistol primers fit nicely into .177 airguns, and engage the rifling just enough to spin them so they hit a brick wall or steel plate cup first, and make a nice "bang" when they hit.