Mossberg JM Pro Failure To Feed

[stinsonbeach]

The first thing to be replaced on the stock 930 should be the cheap flimsy magazine spring. I would replace it with a nordic spring. Also what you have said about keeping the piston clean is right. These guns seem to be sensitive to fouling.

Don't forget to clean under the piston rings....

[ladysaiga]

Ok everybody, I know it's been a long time, but I hit a dry spell competition-wise. After cleaning those rings on the gas piston, the problem did indeed go away based on some initial testing.

The end of this month will be my first match since that time though so we will see how it runs on hard duty-because my Benelli still isn't in a whole month later.

Meanwhile we picked up some AP Custom quad loaders and my new irritation with the JM is that it is NOT ideal for quad loading, and I'm not sure there's any way to modify it to make that work. We need two functioning shotguns for the occasional match where we each need our own gear, and at this time only one of us will be able to quad load-whoever is running the Benelli. Neither of us is much interested in running the SAIGA any more.

While the JM is a very nice shotgun and for the price makes it a good basic entry into tac class, the cleaning takes some extra attention and it is not comfortable for quad loading, so that's ultimately probably going to cause us to phase it out of regular use. Which is too bad, because I really do like the location of the safety on the JM. It's convenient enough to throw it on safe before a reload during a stage, without really taking any extra time or removing my hand from its normal position on fire control. However, I don't think that's a good enough reason not to upgrade to a gun that allows quad loading without pain and irritation!

[HeyChris]

Have you opened the port to allow for quad loading? It also helps to have the lifter welded...

Anyone who quad loads needs to have the port opened on their shotgun in order to be able to do it properly. I've got a JM Pro, have opened my shotgun port and have no problems quad loading... know a lot of others with JM Pro's, who load the same way.

In regards to cleaning, I'm in the habit of cleaning my shotgun after every match, the process is easier than cleaning my AR.. takes nor more than 15-20 minutes tops.

Edited August 17, 2014 by HeyChris

[ladysaiga]

Do you include taking apart the gas piston in that time frame? Because in my opinion, that's the deal breaker. With two of us cleaning two of everything after every match...that's a lot.

As for opening the port, I'm sure that facilitates a bit, but my problem is the abrupt angle of the handguard. It can't be profiled like the Benelli, because it's thin right there, you just can't remove the necessary material.

[HeyChris]

Yes, I include the gas piston... I clean more often than I need to, I think Jerry Miculek recommends cleaning every 2-300 rounds if I remember correctly.

In terms of the handguard, you have to sand that down.. Have you checked out the following link:

http://www.brianenos.com/forums/index.php?showtopic=184530

I have more time than money, so for me the JM Pro was a great buy especially since I like to tinker with things. Opening the port and sanding down the handguard took a couple hours one night.. but quad loading now is incredibly fast easy, I'm still working on the getting fast part. .

Edited August 17, 2014 by HeyChris

[ladysaiga]

I'd like to see a pic of somebody's handguard sanded down. Like I say, I don't see enough material to work with there.

[HeyChris]

Here is a good video that shows you how to do it, just sand it down to fit your use.

It doesn't sound like you like the shotgun, you may just be happier with something else. I'm a firm believer that shooting is more fun when done with a firearm you enjoy, for you that might be with a more expensive shotgun that has all the features you want right out of the box.

[ladysaiga]

Hm yeah, this video sort of shows me exactly why I don't think it's a good idea. In order to make a smooth enough angle, you have to actually remove an inch or so of material altogether, exposing some moving parts. I think I would prefer to stick with 2x2 with the JM and avoid this level of modification.

I don't see much need to bevel the loading port. As is, it's not bothering me.

[Bam Bam]

To quad-load properly, you thumb needs to get past the mag release point without shoving your thumb in the hole. So you do need to open the port forward. If you are doing a strong hand quad load, the side opposite the shell release should be lowered to ease loading.

[Tuflehundon]

Something you may also want to look at is the recoil spring plunger. (not sure of the part name) It's the part in front of the recoil spring in the stock that interacts with the rear tail section of the bolt. I took mine out and it had some burrs on the back of it, like the recoil spring had dug into it. I put it in a drill and ran it against a file and then some fine sand paper to smooth it out and then polish it. My gun seemed like it was running slow.

I fixed that issue and now it seems I also had the carrier latch issue. Getting ready to take it out and polish the front tip of it to see if it fixes my issues.

Mine ran great until I hit about 1000 rounds through her and then she started acting up. Hopefully this last thing will get her running right again.

[blaese490]

My extractor stopped working and had trigger issues. Easy fix..... bought a Versa Max and now have no issues!

[usmc1094]

My extractor stopped working and had trigger issues. Easy fix..... bought a Versa Max and now have no issues!

That doesn't really help anyone.

[IntenseImage]

It doesn't help anyone since I cleaned his extractor (after he let it rust solid) and it was working after that and I couldn't replicate his trigger problem

Sent from my XT1080 using Tapatalk

Edited November 3, 2014 by IntenseImage

[mpom]

Mossberg is obviously at fault here, making a shotgun that requires the owner to clean and lube on rare ocassion. Not.

Edited November 3, 2014 by mpom

[openclassterror]

I have sanded down the fore end for several customers. The trick is to fill in the underside with an epoxy mixture ( I use Max-steel epoxy putty) after roughing it up inside with 60 grit sandpaper. This fills the gap between the fore-end and the plastic spacer as well. MAKE SURE you apply paste wax to the plastic spacer and let it dry before filling the gap, or the epoxy will unitize the two! Once cured, you can remove material aggressively without exposing the spring.

[Tuflehundon]

Has anyone tried the Marine Spacer Tube for there 930's? Supposed to help with the short stroking issues. I just replaced and polished my carrier latch and replaced my recoil spring plunger, which fixed the issues I was having. I went ahead and picked one the the spacers up just in case.

http://www.oregun.com/OR3GUN/about_or3gun_marine.htm

[AirForce2]

Other than the suggestion to epoxy the bottom inside track of the foregrip, then grind and sand to make the quads work and open load port, if you want some pics and details that may help you look at my forum on the JM Pro Review by AirForce2. It should have some details and pics to help you. Pay close attention to the later updates about the proper way to contour the front section of the load port and which way to angle it or you'll screw up your quads for good. Easy to do with some cheap dremel, drill, grinder & grinder bits and polished bits from amazon to finish load port & foregrip. Once you take down/taper the rear and rear sides of the stock foregrip as the pics, you should be able quad pretty well. Keep in mind it was my first shotgun & gunsmithing venture on a shotgun. I also have a pic & description on the thumb entry load port angle comparison between my versamax and the same Jm Pro in my versamax review. Just takes some time and basic tools and for my first 2 shotguns, the only thing I've paid for the work is welding up the lifters (a must) for speed loading.

[mpom]

Has anyone tried the Marine Spacer Tube for there 930's? Supposed to help with the short stroking issues. I just replaced and polished my carrier latch and replaced my recoil spring plunger, which fixed the issues I was having. I went ahead and picked one the the spacers up just in case.

http://www.oregun.com/OR3GUN/about_or3gun_marine.htm

Looks good and it seems like an improvement on the stock item, BUT its twice the cost I would be willing to pay when I don't have any issues with the lightest loads I have (1 1/8 oz at 1145).

Not sure if its intentional or not, but the rusting shown in the video should not occur in the JM, AFAIK, as the mag tube is either SS or nickel/chrome plated. Can see the rusting occurring on a non JM 930, but the video describes issues with the JM.

[Tuflehundon]

I have never been able to run anything lower than 1200 reliably. Put the marine spacer in Friday and was able to shoot 1145's no problem.

[rtp]

I have never been able to run anything lower than 1200 reliably. Put the marine spacer in Friday and was able to shoot 1145's no problem.

Was going to make exactly the same comments as mpom, except for the price - I can cycle 1145s w/no issues in my JM, and the JM mag tube is plated, so not sure where they found that 'rust' from - an SPX, maybe?

Next time I shoot a match in the rain, I'll remember to pull the JM apart, and see if there's any issue there. I like their videos, just not sure it's a solution to a real problem at this point.

Edited November 17, 2014 by rtp

[stinsonbeach]

I've put most of this out before, so I'll be brief...hopefully!

I shoot reduced loads, low brass, 1600 1 1/8 slugs, et al.

NO problems what-so-ever!

Had a JM Pro 24" that took me over a month to get running w/ new springs, etc. Finally figured it out.

Got a 22" new springs, new follower...eats everything.

My take is if you get the new springs & clip to proper length (12-13" past the mag where the mag-extension is going to be) & put in a new follower (800-100-004WB at Brownells). Remember when you were a kid & ALL followers had that "tail"? I'm convinced that is the key...then take the stock follower & put it on the TOP of the new spring & feed it into the extension. Now your spring will not bind.

All my friend's guns that I've done that to has cured their problems. 100% - not a bad track record.

[logiztix]

I know the owner of the shotgun in the picture and I actually took that picture on my phone when I tore the gun down for him over a year ago. It was an SPX that was shot in a cold, foggy match on the Oregon coast and put back in the safe without cleaning. He attempted to run it in a match a month later and it was one big malfunction. The safe even had a dehumidifier in it, but the water sucked in from the humid, salt air stayed trapped between the spacer tube and magazine tube. My SPX has some minor pitting as well from shooting the same matches in the same conditions and failing to clean it until a few days later. Once I learned what was happening, I managed to keep the same from happening to my 930 Turkey by cleaning it as soon as I got home from a match every time.

The 930 JM Pro in the video is his 3rd 930 and exhibits the same problems in foggy, high humidity conditions. The Boron Nitride finish on the JM Pro won't have the rust problems, but the gas system itself is still affected by the coast's ability to fill it with water from condensation as you shoot it. You can forget running it at dew point. With the factory part it won't shoot a full mag tube without a malfunction once the moisture builds up. It runs flawlessly with the Marine Spacer Tube.

Although nobody at the match knew about it, the Marine Spacer Tube was initially prototyped in the Crimson Trace Midnight 3-Gun Invitational by three of us that went about 25 miles inland to train one night and had a whole fleet of SPXs turn into single-shots. We ran pumps as backups that night and tore them down two days later to find the spacer tubes still filled with water. The guy that manufactures the part called me the next morning where we discussed all kinds of ideas for modified 12 volt boot dryers, vented forends, dehumidifier lined cases and 3-gun carts with heated blankets to get us through the match.

We both decided to combine our backgrounds and take a crack at fixing the root problem. The condensation was going to happen, especially at night. We just needed to get rid of it and keep it from dragging down the gas system. We didn't have a single hiccup with our SPXs in the M3GI. Granted, the desert was a bit drier than the coast, but it rained the day of the match and there was plenty of fog at times. A good portion of the match was shot at the dew point.

After the prototypes were 100% successful in testing with other local problem guns, we decided to make a production run to have something a bit more polished than the prototypes. We realized there were others that hadn't given up on the 930 that might benefit from the part.

It's proven a bit tough to solve a problem most people don't believe they have when they have it. In general, troubleshooting the 930 is an effort in combating tolerance stacking. We've found this to be the only issue that is universal with all guns and not a quality control issue from gun to gun.

In the video, the only difference between a fully functional 930 and a single-shot was a spritz of water into the factory spacer tube before reassembly. This simulates what we found when we took them apart after they wouldn't run at night. It would run great for 5-6 rounds and start to fail as the water from condensation mixed with carbon and dirt. We could literally drown the JM-Pro with the Marine Spacer Tube and it just kept working. The only time that MST equipped 930 has hiccuped since is when he tried running 26 Grams of #8 shot at 980 FPS for grins. The failure of about 50% of them to cycle was a smaller problem than the fact the 100% of the poppers were unconvinced that they were shot at.

Admittedly, not everybody needs the part. If you're shooting 3-Gun in Arizona, you probably have no use for it. Every YouTube we saw of the short-cycling problem had someone standing in wet grass with a heavy coat on and you could see their breath when they talked about the problem with their gun. It was quite humorous when we started seeing how either everyone that owned a defective 930 picked a lousy place to live, or there was something to the moisture issue.

For us, it was cheaper to engineer, prototype and produce a minimum run of parts than it was to replace 8 Mossberg 930s with something else. We just needed to figure out what to do with the rest of the initial run we had manufactured. Long story short, we decided against our initial idea of buying another 92 Mossberg 930s.

[Tuflehundon]

I live in FL, about a mile from the coast. Salt water air here gets into everything. It's always humid here. That's why I bought the Marine Spacer.

[mpom]

Logiztix, did you try simply drilling the holes in the oem tube before creating the MST? The holes, and enhanded clearance in the middle of the tube seem to be the major changes. Wonder if drilling holes and lightly chamfering them, would be sufficient. I would try it if I could get a spare tube.

[logiztix]

Logiztix, did you try simply drilling the holes in the oem tube before creating the MST? The holes, and enhanded clearance in the middle of the tube seem to be the major changes. Wonder if drilling holes and lightly chamfering them, would be sufficient. I would try it if I could get a spare tube.

That was our initial approach to the MST, as it would have certainly been the easiest if it worked. Unfortunately, this didn't address the 'dissimilar metals' aspect of the condensation issue or account for how much transient gas pressure is actually trying to get through that part. The tube also continued to rust everywhere there wasn't a hole directly above it while it sat in your safe for a couple days before you got to cleaning it.

The initial 'skeletonize it' approach also made the part structurally questionable once we had enough holes in a matrix to where the part cycling exposed 100% of the tube to the outside world. From a machining standpoint, we also had a lot of cleanup to do with burs on the inside of the tube when drilling through curved material. The burs would drag on and scratch the blued tubes of the SPX. We also didn't see a way to reliably chamfer a hole on a curved surface, especially on the inside. The other thing that caused concern is that we had lightened the part to where we could see on slow-motion video an effect similar to the bolt slap you get when you remove the weight from the buffer of your AR-15. A small quantity of 930s have been shown to develop cracks in the plastic pusher assembly all on their own and we didn't want to create something that could possibly contribute to it. In short, we went through a quantity of factory spacer tubes at $14 each with the initial hope we could accomplish what we wanted by modifying the factory part. It simply didn't happen as the part's primary function hinges more on the relief cut.

The relief cut is actually the primary component, as it creates two sets of right angles around the tube that cross over each other with each cycle, effectively shedding the water. The relief creates 'rings' at each end that are narrower that the distance traveled each time the gas system cycles. That way, 100% of the are under the tube is squeegeed twice or exposed to free air with every shot. Nothing can build up. In order to accomplish this effectively and retain the part's necessary weight we had to start with a larger diameter extrusion than the factory part. The holes do provide the transient gas, carbon and crud a route to escape and allows the 75% of the area exposed under the tube to breathe and dry out after you're done shooting for the day.

As for the cost to produce and subsequent selling price we had to set at this point, we looked at it as a vastly cheaper alternative to a new shotgun. For us, even if we never found a use for one outside of our own guns in our shooting circle, we were money ahead sitting on the rest of the production run if we could make our guns run in the conditions we always find ourselves shooting in. We used to look at things like the Matchsaver and the anodized +5 base pads too and think "it's a 2 second reload folks". We own a bunch of that kind of stuff now, because I have been knocked a few slots down the prize table by less than that 2 seconds. We simply got tired of fixing malfunctions on the clock (even though I got it down to about 3 seconds) and didn't have new shotgun budgets ahead of the M3GI where we new from history that there would be dew point problems. Yeah, I can buy a Glock factory base pad for $2, but I have adopted 'buy once and cry once' to a certain degree and will never start a stage with fewer rounds than I'm allowed. Also, as a lefty that had been running Mossbergs for decades, I don't get along with much else.