I think the OP has a SR556, not a AR556. No gas seals on the SR.I just came back from the local store and they had a NEW AR556. I also talked to their AR specialist to whom I described your pictures.
1) Remove the bolt from the bolt carrier and remove the gas seals. The bolt should move smoothly inside the bolt carrier
2) Once reassembled, make sure the pin travels smoothly and freely.
3) You may try slightly rounding and polishing the edges and of the pin.
Besure you are using a light oil and not grease.