I had some protected 18650's that were tight in my GGT. I cured this with some rolled up paper and some fine sandpaper wrapped round that and sanded the inside of the tube a little (removed the button and caps obviously) and it didn't really need that much work to get them sliding freely
For the sake of those "less handy", let's all learn to use the precise, more accurate term. Nothing personal here, SANDPAPER is for WOOD, EMERY CLOTH is for METAL. If a newbie is reading, and wants to attempt this, and goes to the hardware store, they want to BUY "EMERY" paper, for METAL, it normally looks dark or black in color, and can be wetted with water for smoother working, and comes in various grades. You might start with a coarser grade to bite into the metal more, and finish with a finer grade to make the surface smoother. That should be enough for an internal part no one sees. For external work, you then get into metal polishing, by hand or better by machine for a high gloss.
If anyone is really using wood sandpaper, it could work, but since being made for wood sanding, is a poor choice and while taking down the surface, it would involve more work, more "scratching" etc. I only posted this for those that may not know this, the proper term used here in the US, is "emery" paper for metal work, or even more precise "emery cloth".
