At first, my 25-06 TC Encore barrel gapped .003" from the receiver with
the stock hinge-pin. After installing Mike's oversize hinge-pin, that gap
was narrowed by almost 2/3ds!! I couldn't believe it took care of so much
"slop" in that area -- what a GREAT side effect!
However, the reloads which I had previously matched to the chamber (as
well as the gap, as it turned out) were now a tad too long and required
slamming the action shut. After those loads were shot up, and brass was
matched to the "new" chamber setup, the action closed normally with a
round in the chamber.
Hoping your problem is as simple to solve.