+1 to what 1911crazy says.
Cosmoline is the most likely culprit. Deisel, sewing machine oil ( I don't know where it went honey honest), 3 in 1 oil and transmission fluid are a few of the solvents I have used. If you are able to dis-assemble and reassmble you can also scrub the parts with solvent and a small parts brush. One of the wofe's surplus rifles required that cleaning to cure bolt problems.
Just my 2¢
Steve