Of course 7.62 cal = 7.62 MM
Getting old is a bitch, but it sure as hell beats the alternative!
Sometimes also seen written as 7,62 mm, and on some ammo crate markings as 7/62mm. About the only likely source for confusion would be in naval gunnery, where caliber is also used to express barrel length in relation to projectile diameter, as with the US 3-inch, 50 cal and the 5-inch 25cal. guns- a 7.62 caliber naval piece would have a really short tube, like a mountain howitzer. I suppose the Soviet 76.2mm AT gun caliber could become an easy typo goof, too.
Getting old is a bitch, but it sure as hell beats the alternative!
Surely reasonable people with differing viewpoints can find some middle position and compromise!