Been loading and shooting for a long time,45 years. I always try different primers because primers do make a difference in accuracy. You will not know which primer works best with your rifle, powder, bullet, case combo until you give it a try. I shoot a lot of ARs. In 5.56/223 I have never had any problems with CCI 400s or any of the CCIs, WW, Rem 7 1/2, Wolf mag. Wish I could get Wolf/Tula again. In 6.5 Grendel in the AR I use CCI 450 or Rem. 7 1/2 exclusively because they handle pressure better. Only experience with slam fire I have ever had was with a M1 Garand with Federal 210 Match primers. I learned real quickly not to use ANY Federal primers in free floating firing pin rifles because of their sensitivity. I had a double fire in the first clip in the M1 and I thought it was just my trigger control causing it. Then the next clip I through I was firing a BAR with a three round burst. I was a young man just getting started loading and shooting the M1 and had not learned what one fellow at the range that day came running to me calling cease fire. First thing he ask was if I was using Federal primers in my loads? I said yes and he told me NEVER use Federal primers in the M1 and M14/M1A, the AR had not gotten popular as a target rifle at that time. Federal has come out with an AR friendly primer in the last couple years though.