Thanks, guys, I am still try finding the reason, but cannot find time to range so far.
I shoot this limited for only couple months, 3000-3500 rounds I think. It ran well with factory spring but I noticed muzzle "nodding" thing so replaced with a 8lb spring recently.
The most weird thing on Sunday was on each stage, only the second round from the first mag (random mag) loaded at ready jammed and prevent the slide fully close (maybe just 1/8 inch away from fully close, but just cannot fire), when I take that caliber out and restart the stage, everything ran well and smooth, reloaded another mag during shooting, no problem...
It happened all 5 stages that day, the only thing I did to this pistol is replace a wolff 8lb recoild spring, a henning rod and a buffer. Someone said it might just be a coincident, if so, I think I should try some powerball this week.