[scdavis0]

I was taking it apart to clean it by uncscrewing the mag cap and this small piece of cylindrical metal popped out of the first plastic ring attached to the barrel. Inside that hole is a tiny spring. I had to use a small screw driver to hold that piece of metal inside the hole with the spring in order to get the mag cap back on. The exploded view of the shotgun doesn't seem to mention this. Any idea what the problem is? What is the purpose of that piece of metal, and how can I get it to stay in place when I take the mag cap off?

[curt]

i'm not sure what you're talking about and i'm too lazy to dig mine out but i believe there is a detent pin at the front of the mag tube that engages the "teeth" on the backend of the mag cap. Its purpose is to keep the mag cap from turning under recoil. I've never taken mine out or even looked at it, just noticed its effect as i was removing my cap and you're right its not in the diagram. Don't know why yours is popping out see if there is some staking thats come undone. Take a look, if you still can't figure it out i'll pull out mine and see if i can help more.

[hksw]

"...popped out of the first plastic ring attached to the barrel."

I have three 590s and all of them metal barrel retaining rings.

From what you have described, it sounds like the detent pin for the mag cap had popped out. Does the cylindrical metal piece have a round end to it?

If this is the case, this piece (along with the spring underneath it) is held in place in the barrel ring by having the edges of the hole they reside in peened over by a punch. This is how it appears to me on my samples. My suggestion would be to find a punch of the right size to knock the edges of the hole over the pin to prevent it from coming out. The punch could hold the pin and spring in while you pound the edges inward. Be careful not to punch the edges over to much 9too deep0 so that the rounded portion of the pin is below the front surface of the ring. It needs to be above this surface to do its job, that of preventing the cap from unscrewing by sitting into the grooves of the cap. If the pin is knocked below the surface of the ring, nothing will prevent the cap from unscrewing under recoil.

[scdavis0]

You guys seemed to have nailed what it is. Unfortunately I don't own any tools other than your standard screwdriver and hammer. Any suggestions as to what the best way to do this would be without a punch?

[curt]

a screwdriver and hammer will do assuming that the metal isn't too hard, follow hksw's suggestions and use the corner of the flatblade to make 3 staking marksaround the hole.

If your uncomfortable doing it i would suggest sending it back to mossberg for repair, this is definately a QC problem.

[scdavis0]

I think I'll probably send it back to Mossberg. I really appreciate all of your help.