552 troubles
Re: 552 troubles
Did you pull out the trigger mechanism and thoroughly clean that too? Sounds to me like the hammer is not being caught by the sear and is falling against the bolt as it moves forward. This can be checked by loading only 1 round and then feeling the resistance as you pull back slowly from the forward bolt position. It will be noticeable once you know the feeling.
Re: 552 troubles
Can you pull the trigger mechanism out and make the hammer catch the sear every time?