A change of primer
Q: Will changing rifle primer alter the accuracy and velocity of my reloads?
A: It’s amazing what does and what does not influence the combustion and propulsion of a bullet on pulling the trigger. Sometimes, even the smallest tweak can make a big difference, but other times you can change a load significantly and it will show very little alteration. That’s why it’s important to fine tune a load for each individual rifle when reloading.
Factors that influence performance include components, such as brass thickness; powder choice; bullet dimensions, and, of course, the primer to ignite it all.
The primer is one of the simplest components to exchange in the reloading process and can often make a real difference. Primers burn for different lengths of time, at different temperatures and at varying intensities, all of which influence the ignition of the powder. This ultimately changes the pressure on the base of the bullet and thus affects velocity and potential accuracy due to changing barrel harmonics.
So, if you have a load you like I would recommend buying a few alternative primers to see how they react in your rifle.