The bullet at right is definitely a .45-70 bullet, so its diameter isn't 1/2-inch, despite what the finder says.
As Skeetered said, to identify bullets with
certainty (which theoretically is what the finder came here wanting), we need super-precise measurements of length and diameter. We also need to see well-focused photos of each bullet's side
and bottom. So far we've been given a fuzzy photo and inaccurate measurements.
Because I know the bullet on the right is a .45-70, I've used its "known diameter" and put my caliper onto the photo of the other bullets. Doing the mathematical ratio calculation from those measurements, here is my best guess about their ID:
bullet #1 appears to be a Sharps .44-77 bullet, 1870s/80s -- good guess from a fuzzy photo, Skeetered!

bullet #2 appears to be a civil war generic 3-groove .58-caliber Minie-ball
bullet #3 is definitely a .45-70 "Government Rifle" bullet (smooth-bottomed grooves is 1870s, "reeded" grooves is 1880s/90s)
However, as I said, that's just a "best guess", based on using a caliper on a posted fuzzy, shadow-y photo. To give definite identifications, I need clear photos of each bullet's side and bottom, and diameter measurements in hundredths-of-an-inch.
Edit: Several replies got posted while I was typing mine. The photo of the first bullet's bottom confirms my guess, it is a .44-77 Sharps, strictly post-civil-war. I stand by what I said about the other two.