You are correct and in fact this should always be done every time you change to a different pellet. It is called slugging a barrel. In PBs it is done with a soft lead ball. For the purpose of sizing a barrel. In an airgun ideally you want the least amount of barrel friction with sufficient rifling bite not to strip lead from the pellet. It is the reason most pellet manufacturers make their pellets in different sizes. Just .001" in diameter can make a big difference.With most air rifles, this can present a safety issue. I there is air in the gun, I'd remove the barrel before pushing the pellet out from the muzzle to breech.
I'm a touchy/feely guy and I like to feel the resistance of the pellet or slug passing through the barrel and I usually do not remove the barrel when I do it. After a while with experience, you will feel the difference between tight and loose. Viewing the depth of the styrations is a pretty good clue.
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