Lloyd is right on. Many years ago, a friend and I was out at the range, checking loads for silhouette. His gun was a T/C 10'' in 7tcu. He had scoped it, and we were shooting groups at 100yds.
He was consistently getting under 2'', when all at once, the groups were 4'' and bigger. We couldn't figure out, what happened, when I noticed that the color of the primers were different in his ammo box. When I mentioned this, he said he had run out of one kind of primer, and had finished loading with another brand.(it's been many years back, but I believe that he was getting good groups with Rem.71/2 br., and had switched to standard CCI).
That little experiment convinced me, that what your gun like's, stick with it. gypsyman