Lou, check the receiver lock up faces for set back. I had a Winchester P14 that the bolt was almost impossible to open after firing milsurp MkVII ammunition. The bolt would also close on the max No Go gauge. A learned buddy told me of some problems he had run accross in such cases and told me about the set back problem.
In the case of my rifle, he was right. Somehow the faces had suffered set back. The bolt, which had matching numbers was fine, when checked with filings and a magnet, no faults were apparent.
If there is no set back, cantoms trick will work just fine, so will fresh ammunition.
I have a P17 with out of spec headspace. It is in excellent condition and shoots better than I can point it. It also leaves all brass fired in it with a large expansion ring at the base. I only shoot hand loads with brass fired from this rifle in it. To bad, because it's definitley something a prospective buyer should be made aware of.