failure to extract mr556

So I went to go rezero my mr556 and it fired perfectly the first shot but wouldn't extract/eject and feed the next round. I was thinking it might of been the gas block or piston system but after further inspection there is no noticeable damage or anything out of place. Then I thought it might be the ammo which im using 62grain m855 5.56 but wouldn't that be fine? Or maybe im just an idiot and have to use different ammo? Any input would be appreciated thank you.
SSG Tyler Long