Mossberg 930 SPX

[Not_A_Llama]

Does anyone here own one? I love most aspects of the gun, but I'm having a terrible time getting mine to work with Winchester Universal shells. My old Remington 11-87 Police ate them fine.

The 930SPX also dislikes the 100-pack Federal, but loves the Game-shok bluebox Federals.

I've polished/burnished the chamber, and it's been back to Mossberg once already. Nothing's really changed.

Just trying to get some color on the situation from other owners.

[Daniel_187]

I have one and have dumped around 375rds of variurs cheap wal-amrt ammo and Only had 1 mis feed when i first took it out, and I think it was my fault because i was hip firing it and trying to see how fast it would cycle and did not have it up on the shoulder. Have you taking it apart and put something in the wrong way(yes I have done this with semi shotguns).

[BPTactical]

Check the orientation of your gas piston-be sure it is correctly installed.
I am not uber familiar with the 930 but it is very similar to the FN SLP in operation.
Do you have a "light" and "heavy" piston for it? My SLP would be funky if I did not have the right piston in it.

Define "Not working". Is it a failure to feed-failure to chamber-failure to eject?
It will help give us a direction to look in......

[bellavite1]

There is a nut-like kind of thing that packs the gas tings with a spring under the forend.
If that comes loose it will leak gas and not feed properly.
Get a screwdriver and use it as a lever to tighten it.
DO NOT unscrew it: the spring is really tight and you'll need a couple of friends to compress it enough to thread the nut back on.
Ask me how I know...

[Not_A_Llama]

Sorry for the lightness on details - I've been bugged by this problem for a while, and lost sight of the fact that other people don't know the intricacies. I put a couple entries up on my blog about it ( http://top-quark.com/blog - if you're so compelled), but I'll start tabula rasa here, just to clear my mindset.

With regard to proper reassembly - I think I'm doing it right, by reversing how it came, checking the manual, and consulting a youtube vid. As I mentioned, it went to the factory, where they apparently put a high volume of brass-headed ammo through, and replaced some parts. When it came back, I touched nothing, and took it to the range - it again did not reliably extract the Winchesters (and federal 100-pack). On disassembly, it looked exactly as I had sent it.

The failure mode is a failure to extract - it looks like a lack of gas pressure. In the past, it's also periodically manifested some doublefeeds, but that seems to have disappeared since its trip to the Mossberg repair depot.

On the theory that it's a lack of pressure or perhaps excess/insufficient lube, I've checked and cleaned the gas ports in the barrel and experimented with varying levels of lubrication in the gas system components. There's no different piston weights on the 930SPX.

I have been able to get a maximum of three rounds of the Winchester Universal to function, after adding a light coating of CLP to the chamber - it's sometimes considered dangerous practice on rifles and pistols, on account of increased pressure against the bolt (I was kinda going for that). My other concern was that perhaps the chamber was too rough, and the steel head of the Winchesters was grabbing imperfections. A chamber polishing with flitz on a cloth-wrapped bore mop was unsuccessful at improving function, as was 0000 steel wool burnishing. Maybe it needs even more polish?

What's really irritating me here is that I had a friend who owned a 930SPX, and it'd perfectly eat shells from the same box that mine would puke from. He's moved out of town now, so I can't readily compare/swap parts with him anymore. My gun's still well-within warranty, but it takes about a month to send it in and get it back, and it doesn't really look like they're doing much besides shooting high-power/high-brass shotshells through, which I *know* work perfectly. It's the cheap stuff that I want to shoot, and I know at least *some* 930SPXs can.

I'm hoping maybe to run across someone else with a 930SPX at the range or a shoot that won't mind me temporarily swapping around some parts, just to isolate what's wrong with my gun.

I'll try the nut-like thing. I don't fully understand the gun's mechanism, forward of the assembly, so I'll spend some time to figure it out.

[BPTactical]

Here is your problem:
You are shooting steel headed shells.
Here is the fix:
Stop shooting them.


Brass is an elastic metal and somewhat self lubricating. When you fire the shell the head fire-forms to the chamber and relaxes somewhat allowing extraction, even if the chamber pressure is a touch high yet with a quick cycling action like most gas shotguns do.
Steel heads fire-form as well, only steel is not nearly as elastic so it doesnt relax as much as brass. It is not self lubricating like brass as well. Add to this the quick cycle and trying to extract while chamber pressures are still up there and the issue is compounded.
It also explains why it seems better when you CLP the chamber(Stop doing that too)
This is the same reason steel casings will stick in an AR.
Chances are your chamber is a touch tight compared to your buddies 930.
It can be measured and opened up if need be or you can stay with the brass headed stuff.