After 18-20k rounds my CORE is acting strange. Last few times at the range I have had the following issue. When shooting it seems like the rounds are ejecting too soon. There is a flash visable in the area of the ejection port. Today this happened three times out of about 300 rounds. It clearly noticeable to all watching and I feel powder and ash hitting me in face.

I have both a 9 and 40 spring set and am sure I have the green one in when shooting 40s. I tried the blue spring set today and only noticed a slight change in felt recoil. I am not able to make this happen. I use freedom munintions 155gr rnfp ammo and have had good luck with them.

Any clues beyond replacing the spring?