Bullets (good bullets from major bullet-makers) are so uniform that you could, if you wanted to, use them as a standard to CHECK a mike with.
If it is marked on a box of bullets .451, or .358 dia. then they should be at least a ten-thousands of an inch from that, checked with a micrometer.
I use a dial caliper too as a method for precision measuring but we really should use a micrometer.
Use a micrometer to check those bullets; if they're still .450, then they're undersized for 45ACP or late 45COLTS.'
I think you said they came in a bag???????