FN Herstal Firearms banner

Threaded barrel maintenance

790 Views 7 Replies 5 Participants Last post by  Gary1952
Hello. I am new to FN and recently purchased an FN 509 midsize tactical. It is my first pistol with a threaded barrel.

I put 300 rounds of Remington target practice ammo through it today for the first time. I noticed afterward that the cap on the barrel came loose and that the threads and crown were light gray and brown, as if they had rusted--which I can't believe. But I tried CLP and it is still there.

I have never seen this before on a gun. Is this normal for threaded barrels? How do you fix it? The pictures don't do justice to how light the barrel looks now, even after hard scrubbing with CLP.

Camera accessory Cylinder Optical instrument Air gun Trigger

Camera accessory Camera lens Gas Cylinder Lens

Office supplies Cylinder Camera accessory Engineering Auto part
See less See more
1 - 1 of 8 Posts
What do you recommend I use to scrub it clean? Like I said, I have never encountered this before on my other guns!
Carbon remover

You can also use a die to keep the threads looking new. Word of caution here, try to get most of the carbon buildup off before using the die and be sure to use oil/cutting fluid if you are cleaning the thread up with a die.

1/2x28 Die
1 - 1 of 8 Posts