Raimey,
Unless I intend to load a significant quantity of the same cartridges, I don't usually tighten the set screw. If I only have one rifle with a particular setting, I will tighten the set screw. I use the same set of 8mm Mauser dies to load 8x57 I-IS, IR-IRS, R/360, 8.25x57R Hagen, and 8x72R, so I have to set them for each rifle. On the other hand, the 5.6x61R vom Hofe Super Express stay set the same.
Cris,
The universal decapper doesn't do anything to harm the cases and a factory round fired in a particular chamber can't be larger in diameter than that chamber but will likely be larger and/or different shape than the factory rounds. This is why I set the dies like I do, to make the reloaded cases the same as the chamber rather than a factory round. Custom/ commercial hand loaders need to make cases the same as factory rounds, so they fit everybody's rifle (unless they have the rifle or cases fired in it to set the dies by). If a case fired in a chamber won't go back into the chamber (absent excessive pressure) something has happened during the reloading process to change one or more of the dimensions. When you smoke the cases, you should be able to see what changed. The case length should be measured and the cases trimmed to the "trim to" length (usually a little shorter than new case length). Bulges in the shoulder area are often caused by seating a bullet w/o cannelure in a too long case or crimping too much on a solid area of the bullet. I believe you will quickly "figure" the problem out when you smoke a case. Good luck.
Mike
