I was going to ask you if you were shooting Hornady Superformance, it's been known to give gas guns fits.. Glad you found the issue. I have a first year production SR-25. Back in 1993, I was blowing primers with Federal GMM 168. I called Knight's and was told to keep shooting and the rifle would "settle in". It actually did. The chamber was really tight. Even today, after 2300+ rounds, the fired cases shoulders measure 1.631".
Back around 2006, I was shooting some Hornady 168 TAP ammo and was blowing primers in the SR-25 (SR-25 was a SWAT duty Rifle). I got ahold of Hornady L/E and sent some of the ammo lot back to them. They tested it, sent me some ammo from a re-adjusted lot and it worked fine after that. Gas guns can be very finicky. I also have a GAP 10 that puts the old SR-25 to shame.
You can get the most out of your gun by handloading for it.