This Superior grade 12ga. O/U, functions great when it is cold. Nice and tight and opens firmly. But, by the time I get to the 10th shot at trap, the action seems to have swelled and getting the gun to break open is tough, like breaking it over your knee. It has to be a simple job to stone or polish the action someplace. I have had the gun down many times to clean and lubricate. Nothing seems apparent to me. Any ideas?