Is a 50 caliber bullet measured differently than a 5.56 caliber bullet. if so how is the 50 larger than the 5.56?

They are most certainly measured differently. The "50" in 50 caliber is measuring in inches and should actually be referred in writing as ".50 Caliber." The "5.56" is in millimeters (mm) and should be written as "5.56mm".

To compare the two:

.50 Caliber = 1/2 inch = 12.7mm
5.56mm = ~ .2189 inch

So the .50 caliber bullet is roughly 2.28 times wider than the 5.56mm caliber bullet.