When using powder coated bullets, care needs to be taken to ensure the case neck does not shave the powder coat off.

Any brass that was previously crimped will shave the powder coat, so the crimp has to be removed.

This is done by slightly expanding the case mouth. It only needs a very slight case mouth bell, if you can feel it in your fingers but not necessarily pick it up with your eyes, it's enough.

Then chamfer the case neck to smooth on the inside.

Case anneal is advised after every couple of firings as a preventative measure against case mouth cracks. Brass for big bore rifles can be expensive. Treat them carefully to get the most firings possible.

For .375 and .416 case belling, I found that an old RCBS 38 special decapping rod assembly worked very well. Grinding the end to mooth round, and the steps in it bell the .375 and the .416 brass when fitted to a RCBS 458 case mouth expander die.

My RCBS 500 Jeffery dies come with a case expander.