I had loads worked up for my modified .243 that would cut 1/3" groups at 100 yards all day long.
I switched out the primers for CCIs one day because my gunshop was out of the ones I normally used (Federal).
Groups opened up to well over an inch.
When I went back to Federals, my groups shrank back to where they should have been.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.