All responses sound good. Dan may have hit the problem with the rifle not being 'ultra clean'. On the other hand, I've been too lazy to clean my rifle, only patching it out the next day - no problems, but it was quite dry and it was stored in the truck overnight. When camping in the primitive section, the rifle lays on the 'cooler's' blankets in the open - properly cleaned and ready for loading for the next day's events. By then, it's warmed up from freezing to the 60's or so - sometimes into the 80's by the time we get moving. That's a big temp raise without problems. Rifle always goes off perfectly on the 'fouling' target.