“I removed the decapper stem and applied case lube and run the loaded rounds through”
You did not say “You are not going to believe this....etc..” If you do not give me an option I will take one. The diameter of the bullet is? The diameter of the neck after sizing is....? To seat a bullet after sizing requires an expander plug/sizer ball to be pulled through the neck when the ram is lowered. After sizing the neck of the case with the bullet the outside diameter of the neck was ...?
“Of course that might make some nervous but closing in an action, particularly a semi auto is more jarring than a press stroke”
When the neck is sized down the neck gets longer, when the neck is sized up it gets shorter. I have sized loaded rounds with limited case travel into the die, when loading 45 ACP I am forced to remove the appearance the case swallowed a bullet, meaning my 45 ACP cases must have a straight wall, a bullet that swell the case will not feed in two of my 45 ACP pistols.