The mag tube on my 11-87 sp has come out of the receiver. Can this be fixed? Of course the tube holds the barrel to the receiver and without a proper hold the barrel would leave the gun? when fired?

Hey there do you have any pictures you can post? And is there any broken parts? You may have to send it back to remington.

I believe Remington brazes the tubes into the receiver. My gut tells me that this will need to be sent back to Remington. I would contact their customer support to see what they recommend.