To my knowledge this is usually caused by hammer-follow, or a stuck firing pin.
As the bolt closes home, if the firing pin is stuck it can detonate the primer prematurely.
Or if the trigger reset sear is not catching the hammer and holding it until you release the trigger, the hammer can follow the bolt home rather than being held down until you release the trigger, thus hitting the firing pin before the bolt is fully in battery
That’s wild, you okay? Never seen it before, what trigger group are you using? Check your sear and trigger reset function.
Just using a standard mil spec trigger, used to be using the csgcg but never worked with the cnc bolt.
To my knowledge this is usually caused by hammer-follow, or a stuck firing pin.
As the bolt closes home, if the firing pin is stuck it can detonate the primer prematurely.
Or if the trigger reset sear is not catching the hammer and holding it until you release the trigger, the hammer can follow the bolt home rather than being held down until you release the trigger, thus hitting the firing pin before the bolt is fully in battery