Had the exact thing happen to me. I took my 7mm mag from 1.50" groups down to .80-.90" just from switching from Win primers to Fed primers. When I got into reloading, I bought 6-7 packs of primers and used them for everything. Then Bigcountry gave me the wisdom that once I get a rifle "close" I should tweek it with variables. Primers being one of easiest. Dadgum bigcountry he always has to be tweeking something.
