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Yes I noticed the reduced diameter and have been holding off asking the questions because I didnt really want to know the answer but I will call remsport and see what john can do for me.You may have a problem threading the Norinco barrel. They used standard threaded barrels and then lathe cut the threads off reducing the diameter of the threaded area. You would probably have to add a sleeve of some sort to make it work, could get pricey...
Western MA? Remsport. Call and talk to John. He will do it while you wait.
413-579-1994
Pullman Arms in Worcester, they do fantastic work.