I would look to your lube as the problem. Yes, changes in humidty and temperature can have an affect, but not really much with a good lube. For me, and your experience may vary, but I never found anything that was good about Elephant as a gun powder. That stuff would cake in my barrels, no matter what I used as a lube. Now, I have used it only as a powder in my shotguns, but that stuff would prevent reloading after only a few shots. Back to the lube, make a change in lube. Some lubes just plain seem to cook in the barrel and cause a real problem. Your mileage may vary.