Sat Mar 28, 2020 5:25 pm by SafecrackinSammmy
The S&G 8400 series hasnt been used in US Fed Gov since the mid 1980's and due to its special market, I wonder how old your "new" lock is. Check the casting mound between the bolt and the wheels in the case and see if it has a date code stamped.
The cam itself was not made to be disassembled for service but it may just need wiped out good and new grease applied.
If you are opening the cam with the back cover removed, the cam will tend to over extend and make it hard to retract back to the closed postion.
Those locks normally also had the "Centi-Spline" dial where the spline was adjustable so if its a new mount that could be part of the issue.