Originally posted by Placidity
You wouldn't see two holes in his skulls because his bone skull would've been healed. However, thats the area it would be unprotected by adamantium.Even if we assume the bullet did not enter his brain, if it had hit that vulnerable part, it would've caused a fracture in his skull and also brain damage.
Nothing is being assumed, you're ignoring two vital elements:
1) The bullet didn't enter his skull, it crushed against it, this can be seen
2) There is adamantium on his skull were the bullet broke the skin, this can also be seen, when the crushed bullet falls off.
Watch the scene again, if need be.
To a lesser degree, I HIGHLY doubt they had Origins and it's "adamantium bullets" in-mind when they wrote the script to X2.