NitroX

If you "double check the 'tightness' of every projectile when reloading"
then how do you have problems ? Your two statements contradict each other.

I would suggest getting a slightly undersize expander for your dies.

The other thing to remember is if you have multiple different brands of
brass, this will lead to problems as they all have different neck thicknesses.

Batch your brass into brands and try to keep them together when reloading
so you know what is what and your dies can be set up for each batch.

500 Nitro