1) Good.Cheap,Fast? Pick any two (Have reasonable expectations for bargain bullets)
2) Knurling displaces metal and has the effect of making diameters seem to have more material. Don't measure over knurled cannelures
3) Use an appropriate tool for the job. Dial calipers are good tools but if you are using them to say bullets measuring .308 to /309 are "All over the place"
you have a misconception about calipers.
Try a good Browne and Sharpe,Starret,Mitutoyo,etc micrometer,carbide faces,1 10,000th Vernier,check t against a standard such as a J0-Block,and measure your bullets.
The good news,your bullets are probably much better than you think
Your photo file size is way too big. They are magnified so large I can't really look at them.