I had sent it back to FN for the warranty on getting the Gen2 firing pin/bolt a while back. It then sat in the safe and I had a different muzzle device put on. When sending that out, we had just taken the barreled action out of the 'upper' and then put it back in following all of the torque specs.

Start taking it out and go 50 factory rounds zero issues. At one point I swear I fired 2 or 3 rounds in succession.

Then it happens again.

No reason for it, not doing anything crazy, just happened. Same factory ammo the entire time.

Today I go to load a round after another 50 or so factory rounds, hit the bolt release, and it shoots a round downrange into the berm instantly. Obviously my finger was not on the trigger.

What's usually the issue here / what to take apart and specifically look at?

It’s a feature, not a bug.

I would check for something in the firing pin channel that is causing the firing pin to stick/protrude. Having a small piece of primer extruded into the firing pin channel is one of the problems that the early 6.5CM guns had.

It went into the ultrasonic already and I brushed everything out. Didn't see anything out of place but we'll see.

What I did notice was that when the new firing pin went back into the new bolt, and into the BCG, that the firing pin tip when 'relaxed' (not pushed all the way forward like when the hammer hits it) is already just barely poking out through the firing pin hole in the bolt face.

Is this normal?

Mine protrudes a bit too. A little bit is normal, too much is of course not ok. Do you have a way to measure how much it's protruding?

Don't have a tool for it, plus I'd have to measure when it was basically cocked and closed on the chamber.

However, I may have solved it.

After cleaning everything out in the ultrasonic and a brush, I went out with it again. No slam fires or anything until I had a double.

I decided to look at all of the factory ammo and brass thoroughly as before, I had just looked at the fired cases to check for pressure signs or anything that looked off.

I noticed a few of the primers seemed high to the touch. Took them out and only shot rounds where the primer was seated down into the primer pocket and not flush. Zero problems at all.

I'm thinking the factory ammo had primers that were either out of spec, or at least with the slightly protruding firing pin, were too high for the SCAR.