I never would have thought about the case dimensions being different.
While I don't know the specific measurements, the 22 Mag is designed more like a "standard" centerfire round, where the bullet slips into the case neck, and you can see the front of the neck around the bullet. The 22 LR case is the same diameter as the bullet, with that funky little crimp around the "ball" on the back of the bullet.
So while the bullets are essentially the same diameter (think Single Six barrel), the 22 Mag case is larger in diameter.
Did that all make sense?
