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Hello, and OH MAN!

Yes sir, I loved what I did.

I'm not sure the spring is necessarily the issue. It was filthy in there, almost looking like it was never cleaned (or at least VERY LITTLE). At this point, I have to assume it was being dirty that was the problem, as it operated flawlessly at first, only to then to have me start on the malfunction drills.

There sure is a difference between breakdown/reassembly of the 500/590 and the 930! I knew how many more SA moving parts there would be, but this one has me running back to youtube a few times...
 
Done cleaning and reassembling. Here's what I found out and what I did -

Thanks to The Man JM himself through this video -

The gas piston was seriously binding on the tube, due to carbon build-up (discussed about 18 minutes into Jerry's video). After cleaning everything as well as I could, I took some #0000 steel wool and Hoppes and scrubbed it back down so the gas piston travels smoothly.
My related question - how easily should the piston be able to slide out of the housing (sorry, I don't know the actual nomenclature)? Mine is fairly tight in there, it doesn't just drop out. Should it?
I know there is more than sufficient blow-back to push it out, but with nothing to compare it to, it seems a bit tight to me. I did take the steel wool in there to remove as much build-up as I could, and oiled it lightly.

Next issue -
While at the range, I noticed an allen screw on the rest. Thinking it might be mine, I threw it in my pocket. While checking it over during cleaning, sure enough, it was one of the screws holding down the rail on the receiver (2nd from the front).
I read on here that happened to someone else's (LES, I think), and he had his tech over-bore and went to a larger screw. I don't need to do that, but I will likely go the blue Loctite route.
I mention it because the screws are just long enough to prevent the barrel from being re-seated if they are tightened down all the way (found that out during reinstallation!).
So at this point, I just have it out until I can get the Loctite.

I did notice that there were a couple of roll pins that were VERY prone to falling out. One was in the trigger group, the other in the bolt IIRC. Fortunately, I saw both as they were trying to make their escapes, so I knew right were they went.

That's about it for day 2 of ownership, range time and first cleaning.

HOPEFULLY, range trip # 2 will yield the performance I know it's capable of.
 
Requisite pictures as promised.

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Nice!

,,,,,About that loose trigger pin,,,they sell threaded pins that don't come out.;)
 
Thank you sir, but now I know what to look for.

I'm glad I didn't find it after the fact!
"Oh, sweet! Mossberg throws in extra parts with these things!!!" o_O
 
Piston should come out of the barrel lug freely with very little resistance or dragging. I use a rag with some Hoppes to clean the inside out after shooting as there's a lot of gunk that accumulates in there due to the gas ports.
 
Thank you for the info.
I cleaned it out as well as I could, plus, as mentioned, the steel wool and then oiled. It still seems tight to me.

I'll just shoot it again in the next day or two and see how it is after my extensive cleaning. At least now, I have a far better idea of what I'm doing and looking for.

Thanks once again, to the outstanding cast and crew of mossbergowners.com. I really do appreciate it, gentlemen.
 
Wish you all the best and fun with "our" shotgun.
Had some probs with my but love her meanwhile.
And the 590A1... is on my wishlist for after the Glock 35 (2016) and the Remington 700 XCR Tactical LongRange .300 WinMag (2017)
 
Thank you sir, and the same to you.
I'm hoping/believing these issues will be relatively easily resolved.
I *will* have another 590, or 590A1. They're WAY too amazing to not have in the arsenal.
As for your Remington 700, I have a very special fondness for the M40A1... :D

Enjoy them when you get them!
 
That's an awesome story sniper... But wish it was me instead of you...lol. Nah bro, j/k. And congrats On the sweet score. I am jealous though as i have been looking around at the JM series too but too many projects to finish up first plus I love my 590 to death, yet my 870 is growing on me... It's addicting. But can't wait to get a SA version soon.
By the way. Welcome to MO.
 
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Thanks stigmata!
Ha, yeah... it was kinda surreal as it unfolded for me. Something about this 930 just felt "right" to me. I'm gonna hang tough and see what I can pull out of it. I've been a Mossberg fan for a long time now. Plus, I like fixin' things.

I will have another 590, but more traditional/conventional for my tastes then my last one. Right now, I want to see what my new JM 930 can REALLY do.

Thanks bro, much appreciated.
 
Usmc Sniper said:
Yes sir, 8541 Scout Sniper.
Click to expand...

Thank you for serving Sir.


The pistons on both my 930's move freely. If yours is binding at, there's a good chance that's the source of your cycling issue. When you had the shotgun apart, did you disassemble the bolt? Mossberg usually lathers some pretty thick preservative on their guns before they leave the factory. It's not as nasty as cosmoline, but pretty damn close. We've seen it get into the bolt and gum up the firing pin channel enough to cause light strikes. Just another point of inspection to cross off the list if you're still having problems next time out...
 
LAZY EYED SNIPER said:
Thank you for serving Sir.


The pistons on both my 930's move freely. If yours is binding at, there's a good chance that's the source of your cycling issue. When you had the shotgun apart, did you disassemble the bolt? Mossberg usually lathers some pretty thick preservative on their guns before they leave the factory. It's not as nasty as cosmoline, but pretty damn close. We've seen it get into the bolt and gum up the firing pin channel enough to cause light strikes. Just another point of inspection to cross off the list if you're still having problems next time out...
Click to expand...

Yes Sir.

No Sir, not completely dissembled. I checked the firing pin and spring when I had the bolt and carrier out, and it did appear clean and free of cosmoline or anything like it. But I will break it down again today, and inspect for anything that might be gumming up the channel.

As for your pistons moving freely, would they more or less fall out of the lug if you pointed the barrel up?
I just can't see anything in their fitting after cleaning, that would keep it as tight as it is. It is definitely better than before I cleaned it, but I still have to put my finger in the other side of the lug to push it out, while pulling on the lip of the mating side.
 
Mine won't fall out, and I don't think you'd want it that loose as I doubt the rings would be sealing very well at that point. But, I can simply grab the piston with my thumb and index finger on either side and it'll slide right out. It's goes in and out smoothly, but there is some friction if that makes sense.
 
Another approach is to test the piston fit with the gun assembled, less the forearm. This will reveal not only issues with piston/cylinder fit, but also fit relative to the magazine tube and barrel alignment, which can be key in troubleshooting when the piston fit alone seems fine.

With the bolt locked back and the gun resting on the recoil pad and pointed at the ceiling, try the following:

1) Pull the piston out of the cylinder against the spacer tube, pusher assembly and spring.

2) With the entire assembly resting against the forearm retainer, release the piston.

The piston should return solidly into the cylinder with only the weight of the spring pushing it. If it requires more than a nudge to do so, your piston is binding. This can be due to carbon buildup between the rings and piston, build up on the magazine tube or in some cases the cylinder is canted a bit in relation to the barrel. This last one is a barrel weld issue and is extremely rare, but still a possibility.

William

http://www.OR3GUN.com
 
WNCmotard said:
Mine won't fall out, and I don't think you'd want it that loose as I doubt the rings would be sealing very well at that point. But, I can simply grab the piston with my thumb and index finger on either side and it'll slide right out. It's goes in and out smoothly, but there is some friction if that makes sense.
Click to expand...

Mine are the same...
 
Thank you Sir, very informative.

I did break it down again yesterday just to look at it again. It almost seemed that the piston did come out a little more freely. It wasn't quite as difficult as I remembered it. It did appear that the ease/difficulty of pulling free from the lug was somewhat contingent on the orientation of the piston. Spinning it a few degrees in either direction did seem to make it harder/easier to remove. Not much, but perceptible.
And my magazine tube was badly fouled with carbon when I first cleaned it. There was a solid ring of carbon that made the piston difficult to pass over. Steel wool cleared that up nicely.

I'll be heading back to the range this morning to test, and another thorough cleaning afterward.

Will report back with the days performance, and when I have it stripped, I will test without the forearm as you suggested.

Thank you again Sir,
Chuck

OR3GUN said:
Another approach is to test the piston fit with the gun assembled, less the forearm. This will reveal not only issues with piston/cylinder fit, but also fit relative to the magazine tube and barrel alignment, which can be key in troubleshooting when the piston fit alone seems fine.

With the bolt locked back and the gun resting on the recoil pad and pointed at the ceiling, try the following:

1) Pull the piston out of the cylinder against the spacer tube, pusher assembly and spring.

2) With the entire assembly resting against the forearm retainer, release the piston.

The piston should return solidly into the cylinder with only the weight of the spring pushing it. If it requires more than a nudge to do so, your piston is binding. This can be due to carbon buildup between the rings and piston, build up on the magazine tube or in some cases the cylinder is canted a bit in relation to the barrel. This last one is a barrel weld issue and is extremely rare, but still a possibility.

William

http://www.OR3GUN.com
Click to expand...
 
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