Nice t96. It's a shame the remains of the barrel/ receiver weld were not removed during apparent reactivation. What is condition of breech/chamber of spare barrel? Breech end of barrel in gun appears to have been extended. Two original mags is really nice part of the deal. FWIW
Yes, that is a good observation, and likely if it was brazed, but braze does not penetrate the parent metal and it would be brass colored. It is, in my view, the remains of a penetrating weld using stainless steel rod or similar and not a mild steel rod. Stainless weld doesn't not take park.