Might be worth getting a smith to check to see if it is undersized. Ruger will fix it if it is. If it isn't, make your ammo fit it. I use a Wilson case gauge on all my sized 9MM brass. If it fails to enter the gauge (Not often), or fails to fall back out of its own weight, I scrap that case. Ammo loaded with that brass never fails to chamber in my tightest 9MM chamber. Use the "plunk test" to be sure the bullet isn't getting jammed into the lands causing chambering issues.