82's were made in both compositions copper the first half of the year and Copper plated zinc the last half of the year. The zincs weigh 2.5 and the coppers weigh 3.11. Yours are within tolerance levels.
The only one they didn't officially make was the 1982 D small date copper. These would be in the 3.1 range for weight. For comparison, the only small date you have is #1. The others are all large date 82s.
