Gunsmithing TRG-42 Barrel joint

[SSG Mac]

All,

I have been working on a TRG-42, and noticed what appears to be HARD debris at the top of the front action screw (and in the chamfer at the rear of the barrel) It looks like solder!?!
Does anyone have any idea what this might be? This appears to be the factory barrel, as installed.
Any help is greatly appreciated.

 

[ChadTRG42]

Re: TRG-42 Barrel joint

Picture?

 

[usmc7980]

Re: TRG-42 Barrel joint

New rifle, used rifle?

 

[SSG Mac]

Re: TRG-42 Barrel joint

Sorry, no pic available.
It's a pretty well used gun FWIW.