Does changing the primer in a load change the ballistics? When I bought my custom rifle the builder figured out the load for the rifle and gave me 50 rounds. Now that I'm set up to reload I cant find the primers locally. He was using CCI 250's but the local Cabela's never has them in stock , they put 10 boxes on the shelf this morning and they were all gone by 10:30 when I got there. What happens when you change primers? Thanks Allen.