Primer Changes for Shotgun Loads can make a huge difference in pressures. Not so much in Pistol and Rifle, though I agree that if you are looking for the maximum accuracy, I do not change what I load except for things like Federal 205 verse 205Ms which are just the Match version that goes through more inspections.

For pistol I don't care, but would not mix Magnum Primers with non-Magnum. For Benchrest Rifle, I height sort them, then weight sort them and use a dial micrometer seater to get the manufacture's recommented "Crush" when seating them.

Bob

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Sag Harbor & Manhattan, N.Y.