I am having similar results. I suspect copper fouling is the culprit. I'm getting accuracy loss after 30-35 rounds in a 7mag 26" Kreiger that produced excellent and consistent results with 162 Amax during barrel break-in and load development. Then I received my 162 & 175 ELD-Xs. Accuracy was good, but fell off after thirty rounds in barrel that was squeaky clean to start with. I started cleaning powder out every 10 rds and it did not help. At the same time, a 280 Rem was going 100+rds. prior to needing a good cleaning. I was cleaning 7 mag with BoreTech and getting more copper than that barrel ever produced. I was aware of the longer bearing surface and that might explain the quicker copper fouling to some degree, but it's my guess Hornady is using a softer jacket material for better expansion. The 280 was on a diet of HBN coated bullets and did not suffer the same heavy coppering problem and cleaned up real fast. My intention is to run HBN coated 175s in the 7 mag. I have the barrel cleaned and pre-treated 162s and 175s coated and ready to test. Both barrels are 9 twist, 4 grove 26" Kreigers. I suppose the 7 mag version may not have been lapped properly or it hates the 175 ELD-X. Hoping the HBN will make a difference. JMO. I was borescoping both barrels before, during and after cleaning. if it continues, it's back to Bergers.
