When i was in the Service, we used BreakFree CLP. Ive been using it ever since and it works well.
there is other stuff out there thats works too, but i got used to the CLP and thats what i like.
I too have one gun from NEF that was rough, the barrel had light rings to it, but i just 'sanded' them out with steelwool and some cold blueing.. no problems
glenn