Scoring on the Mag Tube

As far as people having issues with the scoring on the mag tube when the barrel is unmounted and mounted, I can just about guarantee that it is a metal ring "inside" the barrels gas port tube.

If you were to disassemble that large front nut on the barrel, there is a large HEAVY duty spring. Under that spring is a steel ring, chamford or tapared on one side. That tapered side should be facing towards the chamber or rear of the barrel, while the flat part should be against the spring to support the springs surface area.

While that barrel nut is being tightened down, that tapered steel ring can easily shift to one side or the other. Off center is the best way of saying it I guess. This can easily cause a slight barrel misalignment and scoring on the mag tube as you install/remove the barrel. If it is correctly centered, the barrel will slide on and off easily.

I had to loosen the barrel nut and use a large screwdriver through the tube and gently pressed against the rings edge with the side of the screwdriver to center it up. The first time I tried to install my 24" slug barrel, I couldn't even get it on because that ring was out of alignment inside the tube.

I will add that due to the strength of the spring, unless you have a plan to put it back together, I don't recommend taking it completely apart. It is very difficult to get back together again. I would just loosen the nut until I could move the ring inside. Hope that helps someone.

Paul

Thanks for the information. I will have to tuck that away in the memory banks.

thanks for the FYI!

I was getting some light scoring(more like scratching)on my 930SPX magazine tube causing some interference when removing or installing the barrel. What I did was go to Lowe's and find a wooden dowel as close to the diameter of my magazine tube as I could. With the gas piston out of the gas cylinder I inserted the wooden dowel and moved it around to center what ever was out of alignment when I heard a click. I’m thinking want ever was out of alignment went back into place. Not sure what I did but all I know is my barrel is 100% easier to remove or install. This little issue in no way effected the performance of the gun. Except for a few hiccups I caused my SPX as been running 100% from day one.

I thought I would take my response from another post, under section "Mossberg 930 Autoloader" - "Can you post some pictures of your mag tube wear?" because even though it is a fairly old thread, it still had almost 500 views which tells me there are quite a few people curios about the subject of other types of wear on the Magazine Tube and post it here also because some people are also concerned about the bluing coming off on their mag tube where the piston rides.

Hopefully this thread will now answer pretty much anything our users may experience with wear on the Magazine Tube.

"My Gas piston catches on the edge of the Magazine Tube Cylinder"
The piston catches on the edge of the Gas Cylinder because as the gun is fired, the piston moves back approximately 3/4 of the way which results in the two parts wearing in together and is perfectly normal since it doesn't slide in and out 100%. There's bound to be a lip on the barrels Gas Cylinder at the edge on a well used gun. If you would like, you can manually take the Gas Piston and work it in and out of the barrels Gas Cylinder until it rides smooothly or even polish the Gas Cylinder on the barrel. This is also recommended for new barrels to make sure you have smooth operation of the Gas System. I don't recommend using oil on the rings of the Gas Piston because the oil will trap more of the carbon that is in the gasses coming through the barrel as the gun is being fired.

"The Bluing is coming off of my Magazine Tube"
The bluing coming off is due to high temp gasses and abrasives (Carbon is the hardest substance on earth next to water after all) from the powder along with those substances being scaped along the Magazine Tube while the piston is being thrown back with enough force to push the bolt back hard enough to overcome the tension of the return spring to eject an old round and push in a new one. All happening in about 1/10th of a second. But this kind of wear is normal.

"My magazine has deep scratches"
Deep scratching of the Magazine Tube is NOT normal and would be caused by the alignment ring inside the barrels gas piston cylinder not being centered and is explained in the previous threads. But it is easily fixed too.

Now go have fun. Not everyones weapon is going to be the same due to springs and mating surfaces. Manufacturers design and build every part with a tolerence of + or - and usually check by parts sampling to ensure that the parts they are producing are in conformence of their design expectations. As long as the parts meet that tolerence, they let it go.

Lastly, many of our shotguns fire more rounds in a weekend with tremendous force than most weapons fire in their entire lives. They DO depend on the manufacturers of the ammo to produce high quality ammunition to use but have no real control of that portion of the gun. A shell can have a couple of grains more powder or less than the shell next to it in the box. Or it could actually be bad and out of tolerence but wasn't caught. That wouldn't be Mossbergs fault now would it?

Regardless. Use quality ammo. Understand completely how your gun operates and keep it clean and in good running order and you will have years of fun and even a sense of security. FWIW. It's just my opinion and we know what they are worth.