thanks for that great pics
Looking at the pictures at the start of the tread, the penetration looks all wrong for a high velocity projectile. Looks more like a pressed or hammered through hole as the metal all goes in one direction and there is no spalling around the entrance. Those examples were likely created in a workshop and not at a firing range and aged afterwards (IMO).
interesting thread ,i must be living under a rock as i havent heard of this kind of thing before ,but it takes me back some years as a child i questioned my great grandfather over his strange looking thumb scarring ,i recall he said he was hit by a turkish sniper bullet during the gallipoli campaign, but anyway back to these coins i would say simply striking these with a stamp punch ,then pushing through a bullet would amount to the desired effect ,a novel display piece but for originality ,best to avoid