Some powders require a tight bullet to burn properly. Usually will lose some velocity with loose bullet.

As for depriming live primers, I usually deprime as a separate operation. I screw the deprimer stem down so that the primer is pushed out before sizing starts. That way I feel just the primer getting pushed out. Push slowly and gently and wear glasses. After depriming put depriming stem back to proper position and then do the resizing.

Hart

Well, if your bullet is too loose, then you are bound to lose your bullet...

I consider any bullet I can push into the case without a press to be too loose. My test is to put the nose of the bullet against a table and push on the case to see if any movement occurs.

A loose round is not always unsafe to fire, but will probably be low on the velocity and accuracy scale. Neck tension is important to holding the bullet in place while the charge burn begins. If there isn't enough tension then the burn may or may not be consistant from round to round. Also, with small cases small bullet movement into the case can result in a major pressure spike. This is primarily a problem with pistol cartridges. I believe my Speer manual noted that a 1mm (0.04") increase in depth put 9mm rounds into the 60k PSI range and strongly warned to watch depth on them.

You can get away with a bit less tension in single-shot rifles, as the round won't get banged around as much as in a magazine under recoil or in an autoloader's cycle.

If your bullets are always loose, check your sizing die and ensure that the expander isn't oversize. If it is, you can turn it down a bit or replace it with a slightly smaller one (or replace the sizing die - they are pretty cheap anyway).

I would worry about the bullet being pushed in. Bullet setback will cause higher pressure.

I have deprimed more than a few rounds without have the primer go off. I have a massive reloading press with a hole for the primer to fall out in the bottom. Worst case scenario for me was to damage the decapping pin. I never had a primer go off. You situation may be different.

Just fire them, safest way to do it. A primer anvil reached 1400 fps in a test I once read, that will take out your eye for sure, be careful.