1 shot how often do you run your car on solid fuel and how often do you shoot lots of bullets through your muffler. I am asking because I want to know. I think the issue is not exclusive to cans, my muzzle breaks also get very tight. No matter how much grease or never seize I use they will still get tight if you don't remove then often. I generally have tools to break them loose but, it puts a lot of strain on the bedding unless you remove the action, and taking the action in and out of the bedding wears it also. I suspect it has to do with the direction of the threads and every bullet tightening it just a tiny bit more. But I would like to hear it from somebody that really knows. Speak up please Dave.