I took my new 930 appart to clean and lube it. The barrel was a bitch to get off. It took forever to get it on. i nothiced that a ring had got stuck in the cylinder in the barrel> from the instructions I am assuming it is the seal ring that is in front of the piston. I did notice it has a split in the ring and is not one full ring. is that normal or did i break it?? thanks

FIXED IT, TOOK IT OUT TO SHOOT........cycles flawlessly.....everything!
Ok..........now the mag tube will omly take 6 round???????WTF
First few mag loads took 7 rounds, once it only took five rounds, now it only loads to 6!!
Come on, any suggestions??

Got a picture?

I have almost the exact same problem and posted this at Tactical Shotguns (the photos are available if you are registered on THR - I cannot figure how to get them posted here:

I disassembled my SPX when I first received it some time ago.  I discovered a small ring (no more than 1/16" thickness, split ring, that fits the OD of the mag tube precisely) that came out of somewhere when I removed the gas piston assembly.  Here is a link to a fellah who is now having the same problem, but with great pics showing the exact small ring I too am speaking of: http://www.thehighroad.org/showthread.php?t=534358.  When I reassembled, I assumed this small ring was the gas seal described in my manual, so I slid it on the mag tube in front of the gas piston per the manual and assembled the barrel over that.  

Well, at long last, I finally got the SPX out to fire for the first time yesterday, putting about twenty slugs through to sight it in.  It seemed to cycle fine, with one or two FTE.  When I followed up with Federal Tactical buckshot however, it absolutely would not cycle!  Worse, upon disassembly, I could not find that small ring!  

Well, last night I discovered it pushed into the large piston spring area in front of the gas ports, wedged behind the gas seal that is pressed behind the large spring - this clearly accounts for the lack of pressure to cycle!  In order to remove the gas piston spring assembly in order to remove the wedged small ring, I tried to remove the large retaining piece/screw with a tool that fits, but it won't budge.  Any advice there?  

Once I get that off and the culprit unknown ring removed, I know I am in for a hassle to replace it per Smitty in CT here: http://thefiringline.com/forums/showthread.php?t=390408, but I have no option to remove that wedged small ring.  I still need to know where the hell that small ring was supposed to have originally gone, as it certainly wasn't supposed to go where I put it!  

Thanks in advance for any and all assistance.

Just spoke with mossberg, they say it pushes on to the front of the piston...not in front of it. It does fit there I had it there last night, but I was not sure if went on or in front of the piston. So mossy says on the piston, ill try it ans shoot this weekend

Try these videos///the best on the net for SPX breakdown and reassembly. Yes I have an 930 SPX, very informative videos. I took my down and reassembled before shooting, no problems whatsoever.

http://www.youtube.com/watch?v=XKpNy2AZzN4

http://www.youtube.com/watch?v=vclvnZo_VoY&feature=related

anyone have this problem???

I've seen these videos and they are helpful for a new owner - unfortunately, they show no detail of the gas piston and seals or the seal behind the recoil spring in the area below the barrel in front of the gas ports.  I found that the thin split washer at issue fits perfectly in the groove of the gas seal that is pressed behind the large recoil spring.  It not only fits, but is seems to make sense that it should be there.  I cannot understand, though, how it would come out upon normal disassembly.  This mystery spit washer will not fit in the inside groove of the gas seals at the front of the piston.  Awaiting time at the range...

UPDATE:  so I placed the mystery thin split washer inside the gas seal that is located immediately behind the large recoil spring in the area in front of the gas port chamber (you must remove the large recoil spring in order to remove the seal there, but it was the only way I was able to extract the wedged split washer).  It fit perfectly, with the split washer having enough room for a small gap at the spit, but such that it will not come out without intentionally removing it.  (Somehow this washer must have made its way out of that area when I initially dissassembled the gun for cleaning and inspection after taking it out of the box.)  The inside diameter of the seal and the spit washer is perfect as well and the inside surface of the spit washer is flat and a perfect match to the flat inside surfaces of the seal.  

After all this, I put 44 rounds through the gun yesterday without a damned hitch, slugs for sighting in, Federal Tactical 00 buck regular and reduced recoil, Winchester 00 buck reduced recoil, some #6 and #7 shot, and not a hiccup.  Dissassembled for inspection and all was perfect in the gas and recoil spring areas!

Also, this is an early SPX with the first LPA front sight.  No cant at all.  Further, although I did raise the front sight post quite a bit to zero, I still have room for upward adjust while the top of the front sight appears in the upper third of the sight protector ears.  Damned lucky after reading all of the early SPX woes.  Regarding sighting in, I noticed that the sight picture for me was a bit tricky in that the dot at the top of the post of course must be in the center of the ghost ring, but the protector ears tended to throw me off a bit, causing the front sight dot to be placed a bit high in the picture.  I worked that out and actually lowered my front sight post.  50 yds and 100 yds with no hold over, dead on!

My SPX and I, although off to a troubling start, are pressing on with what looks to be like a great relationship...