The first question would be when you shut the action and it locks into the closed position is there a lot of movement between the barrel and the receiver? If so that is in most cases the issue. Too much head space and the casing is swelling. I am assuming it is a breakdown model not a bolt? Some pictures would be good.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom."
-- John F. Kennedy