It has got to be one of two things:
1) Chrome barrel is plated and the silver seen here is some excess (chromium) on the chamfer to the extents of where the mask was applied at the muzzle face.
2) Someone chamfered the end of the barrel to clean something up. The silver seen here would be bright base metal (steel).
I was leaning 100% towards GG's thoughts initially, but looking at it more closely I guess it *could* be chrome. The thing that's throwing me off is the dull bluing at the tip of the barrel, almost looks like paint. From the linked post, it sure looks like that barreled action was certainly stripped and reblued with the typical washed out looking light grey bluing resulting everywhere else on the barrel. Maybe it was a BBQ refurb that someone stripped for some reason?
Additionally, if it was a chamfer breaking through to the base metal, you'd expect this unprotected area to start oxidizing pretty quickly, but the photo shows a fairly bright surface.
I pulled a select few muzzle shots of various carbines in the database. I think w/o seeing inside the bore, it's tough to near-impossible to really tell from a single photo what is going on with respect to any chrome plating.
Bright muzzle all the way across the face with a bright chamfer off a pristine as-issued '55:
I would call this one 'counterbored', off a light refurb '54, note the light oxidation:
Heavy chamfer with fully blued face off a pristine as-issued '54 carbine:
No chamfer but bluing worn off at the muzzle and oxidation you'd expect to start seeing as a result off a light refurb '51: