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Mossberg 930 JM Pro Setup/Fixes


AirForce2

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This is info that may help some of you get most of your "JM Pro" items in one place. This is my first shotgun ever and your personal results or professional opinions may vary. These are "my" opinions and findings. They will help many people for sure. I did shoot USPSA for 9 years limited and open ranked A class. I 've usually found that many parts could be better and learned to "optimize" things to function better or to my taste and this new shotgun is not different. I always seem to the the one built on a Fri or Monday hangover. Mine is the 930 JM Pro, 22 inch 8+1 (9+1 w/XL Nordic) and has about 250 bird loads and 50 slugs:

-Length of pull reduced 1.5 inches: Mine is 13 inches from cocked trigger to mid recoil pad. I did not reduce the recoil spring length or tube length of the spring housing section.

--How: 2 items will remove 1.5 inches of the length of pull, one is a low profile limbsaver Model 10544 grind to fit recoil pad (5/8 inch thick, 5 1/2 X 1 31/32 grindable to 3 7/8 x 1 11/32 & rest is stock/tube/spacer mods. 1st remove the orig recoil pad. Determine how much lower the alum spacer can be trimmed/grinded down so as to still allow threads of the recoild spring tube to be just below alum spacer. Also measure how much tube threads to remove so that appx 1/3 thickness of the nut will tighten over threads. Once remove nut, alum spacer and w/grinder remove two thirds of nut height (appx). Grind down the alum spacer removing appx 1/4 to 1/3 height. The nut is not easy to find at local hw, so be careful and make sure you debur the sharp edges on nut & alum spacer. Once nut, alum spacer complete, and recoil tube threads cut off, install everything except the recoild pad and using stiff tape of item to mark straight line on stock, mark line on stock so top of recoil tube is 1/8 to 1/4 above the line you will cut the stock off (to get 13 inch LOP, you cannot cut to much of the tube off or nut, spacer and tube would have to be cut to far). I used a band saw and a leveling device of your choice and went slow w/little pressure so blade didn't bend much. When you are done, without the low profile limbsaver pad, the tube & nut should be just sticking out above the stock. Install the limbsaver pad (orig form), you will need to redrill one new hole in the recoil pad to install to stock and using scribe, mark around the now cut down stock. Remove recoil pad and grind to match stock.

-Sights: If you gun shoots slugs to high or left and you just want adj sights, you can try one option that works and another that I have read about but not tested. Use a tall front sight and add rear adj sight or you can try to see if barrel clamp removal fixes the high shooting issue.

--My fix-Use pliers and untwist front sight. Order TRUGLO Tru Bead Turkey Extreme w/ghost, universal PN TG950XD front & rear sight pkg. This pkg has multiple screws and will fit the Mossberg 930. When installing the front sight, I suggest using some good JB Weld under the base since there is only one screw holding the front sight on & use a good Loctite ( I like to mix red/blue and I don't plan on removing the sights) but don't trust blue enough. Install the rear sight as far back on the rib while still having even pressure on the rear mount plate. Use good locktite on the 4 rear base screws. The rear is adjustable up/down via one screw that with tension screws in or out to raise/lower rear sight. The front sight is 2 colors green outside and red middle. Front sight is large but if you aim/hold properly using the top of the front sight in middle of object to hit, no problem. The front sight is twice as high or more than the orig. My RIO low recoil slugs group inside a std mouse pad at 100 yds and my bird loads at 20 yds pattern spot on with these sights. Fiber optic pieces are known to break off the end tips and then the whole fiber will slide out of the sights ( I know). Use a good "clear" epoxy for light gathering and apply epoxy around the fiber optic tubes enough to meet the metal around the fiber, this may allow the fiber tubes to stay in the front/rear sight holder better in case you bump a prop during recoil or during dumping.

Ext Tube: Many complaints of the tube connect joint is uneven. This may/may not be a one item fix. Mine didn't appear to jam during live fire, but it's like having a bump in your piston wall (can't be good, can only hurt). With barrel clamp, tube ext all tight, remove the end cap (buy a Nordic XL for +1) and w/flashlight look down tube and rotate looking for high spot typically on on side only. Determine if it's the chromed tube of the Mossberg sticking up or the Nordic ext tube and you can dremel/polish this side down and try to loosely slide spring/follower down. Some have said to loosen the Nordic tube nut and rotate the ext tube and this may even up everything, I don't like leaving it loose, but also ensure the barrel clamp is not causing the issue by pulling/pushing the tube up or down causing the alignment issue. In short a combo of sanding the angle of the front foregrip/stock where the nut tightens, polishing down the rear chrome tube and minor polishing of the underside of the Nordic barrel clamp is what mine took. What a pain in the rear. I also have a GG&G follower, but others should suffice.

Tube Spring: The tube that comes with is thin and seems ok, but I replaced with a noticeably stouter Nordic spring and have it at 12 inches past end of ext tube. I suggest you curl the tips on both ends of the spring (follower & end tube) and round/polish the ends so the spring doesn't twist or bind when removing the tube cap (could cause some problems w/spring wrap).

Load Port Opened: Dremel or file and sand the openings on the side and the front. Take care on the side that holds the small pin visible from the bottom and don't grind down to far of you'll hit the section of pin that holds the shell stop/bolt open item in place. Polish the alum with fine eraser type dremel polishers or 2,000 grit sandpaper to taste. You need to also remove & angle the forward load port since this is the primary area that will prevent double/quad reload speed. Grind out wide & forward enough but do not go into the follower stop areas or your going to pay for new receiver. Also grinded down the front grip area forward of load port to help with reloading. I've only been loading a shotgun for a couple of hours and I feel like a monkey doing a football versus loading a semi pistol.

Firing Pin Spring & Trigger: There are far to many complaints of fails to fire on this weapon so before I even shot it, I replaced the firing pin spring w/the Ruger 10/22 (extra power I think) and cut about 3 coils off. No ignition probs in 350 rds.

Stipple grip & forward grip-My first time, but just using a stock little soldering iron and pointed tip made the grips much nicer to hold and for flipping the gun for reloading. Took about 3 hours for me and was quite annoying to do this long (next time will cut the sharp tip off and use a larger rounded profile tip). Don't use big gougy pits or it's gonna stay stuck with all kinds of sweat, dirt, oil, food. You will like the look and feel.

Shell Stop Assembly & Lifter-What a pain these items can be. C-Rums did a good job on the lifter. Before I got this gun I'd read about the scattered issues and knew I'd get the one with at least half of the reported issues. I had some double feeds, rounds would not come out of the tube, gun would lock open when the tube still had shells. All during live fire. I think the combo of rounding off the forward shell stop, rounding off the rear (by back of lifter gate/port bottom side of shell stop (part that locks lifter) and tweeking the lifter a little more to the opposite side. This is not always a one polish piece fix as I've determined. Several areas of the shell stop ie...front side to the tube, back side shell stop that could be hitting the lifter, or lifter is cocked to one side a hair to much can cause the issues listed.

JAMS/MALFUNCTIONS: Many have stated you must fire 50-100 high power/full load/magnums or some crap. Look, it's just a semi-auto. Do directions ever state a brand new pistol needs magnum ammo for first 100 rds, no just std ammo? Problem w/shotgun ammo is your ammo can be 1150 fps or 1350 fps which is a big diff in power for same weight projectiles. After about 100-150 rds you gun, metal parts are pretty much broken in. If you have to shoot 500 rds on any gun to "break it in" the gun specs/tolerances are the problem. One thing I've notice is some loads may eject the spent casing but will not load a new round because it never released from the tube. I think the bolt comes back far enough to eject the casing but doesn't come back quite far or hard enough to release the shell stop. This could be the gun cycles and goes click and when you rack the bolt it loads fine. It amazes me that no aftermarket companies make hardly any recoil springs (except a few browning & benneli) in less or more weights when there are options for AR's & semi pistols. The rear recoil spring has about 96 or so coils, so I'm going to try the puss loads (1150 fps) with appx 10% of the coils cut off now that my gun is broke in. I cut off 9 coils and will see how this works. Don't want to do to much since this spring is crucial to feeding shells in to the chamber as well as recoil control and when using magnum or hot loads keeps from beat the gun apart.

Chamber & internals: I rounded & polished the chamber opening, extractor hook ends, barrel extractor groove cut down deeper and more forward & polished. Polished any hard or rough, peened areas felt after first 75 rds.

-The forward chrome part of tube threads had gouges on one side just like some online reports. I believe the fix is to dremel down a steel O-ring joint about 1/3 up into the barrel part of gas chamber (run your finger up there and look for the o-ring where it would almost come together). If this doesn't fix it it's in the chrome piston area, but it puts a nasty line down the threads and the chrome upper tube.

Side Saddles: Put a GG&G side saddle on and immediately had function problems. Surprisingly, not much online as to why, hence why I was also surprised people use lots of Velcro versions (now I know one reason why). I have the answer. If your side saddle requires removing the trigger housing pins and replaces with screws or pins that will screw from one side to the other side into a nut or into a thread on the other side, Tightening the screw/nut can cause the bottom of the receiver to pinch/bend inward causing cycling problems, slight receiver bending, pressure to trigger/lift gate area etc... I used longer screws but only slightly firm and the other side nuts built into the side saddle and additional pressure nuts on top of that to prevent backing out. I also made my own version of a device similar to what a matchsaver shell holder to hold the one OH s---? round. Bought 5-6 ft length of PEX tube 3/4 inch is all I can find and some counter sunk screws and nuts and velcro I made 2 single shell holders, one for each side for $15 for both and still have tubing to make 15 more with a band saw and dremel and could make about 20 of these and cost is about $3 bucks on a stretch, likely half that in materials.

-Briley Light Mod ext choke

-AP Custom 4x4 (don't like grabbing the rear 4, but good for space)

-Carbon Arms FLS 8's (ok but I need a few more months to see). Quad loads & petting is tough to do fast, so could be need more practice time or these sryle, not for me. Hope this helps some of you.

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Also, when I cut down the stock I just tossed the aluminum spacer completely. It required rethreading the recoil spring tube, but it took the lop down as far as possible without having to futz around with special springs.

Edited by BitchinCamaro
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Very nice write up. I recently got mine back from Mossberg after having the barrel replaced. Before I sent it in I had No malfunctions in 1500 rounds. But i had already completed all the work you stated. Got it back and had the bolt lock back 5-10 percent of the time. Discovered they replaced the shell stop. A little more work, and she is back to normal.

Used her this past weekend in a match in GA. She got soaking wet, and muddy and still ran like a champ. The other shooter in my squad running one was not so lucky. FTFs and double feeds non stop.

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Additional info my post on the Tube spring. I just recently swapped the stock spring for the Nordic and the Nordic version is way stiffer than the skinny stock one. I cut the Nordic spring at 11 inches past the extention tube and even with the XL nordic end cap, barely got 9 rounds of buck shot, didn't have to force #9 but no extra play. Nordic I think recommends 14 inch past the tube and I think this is a little much for a speed loading setup.

So far I've put 200 rds thru my JM Pro including today's 50 rds of 1150 fps remington gun club ammo after cutting 9-10 coild off the recoil spring in the stock. So we'll see if my hours of rookie shotgun smithing works. I forgot to mention I was on the original Air Force IPSC Shooting Team 1997-1999 #2 guy. I was A class ranked, but shot like a master half the time, but screwed up enough big matches over the years to never really get bumped up and didn't care to blast away at a classifier 10 times in a row just to get bumped up.

After being out of shooting since 2000, and all the gun law & Obama ruck lately, PO'd me to get back in and now will dabble in 3-gun. My setup is

-AR CMMG M-4, 16 in std barrel, JP Bolt, silent capture spring, JP EZ Trigger, P mags, UTG PRO Slim Rifle length foregrip, JP Adustable low prof gas block, SJC Titan on a budget throw lever get 2 breakaway coaster cat tails for $20 shipped vs $50 for a real one, $40 offset iron sights (they work for good out to 100 yds, we'll see if they hold up to rough housing)burris MTAC (lighted reticle useless during day as with all AR 1-4x optics) unless to pay $1,000 or more. Are you guys getting this ie...Burris, Vortex, Millet, Bushnell. They have good reticles but not daytime visible. Nobody has a daylight visible reticle 1-4x scope under $500 (cloudy/overcast day doesn't count). Even a $30 red dot scope is pretty visible during daylight. My AR is the most reliable of my new 3 gun setup so far.

-CZ Accu Shadow-Gun was pretty good from CZ Custom. I only did a minor polishing/contouring as the ramp enters the throat. Only just started shotting it since late Feb and function and accuracy seem good so far. After 150 rds break in my 100 yd 5 shot group only bottom of handle on sandbag was about 6.5 inches with just some remanf Ultramax 9mm 115 gr and should be better w/pet loads. Like I figured, the Accu Shadow's great feeling single a double action can be fickle at the price of harder primers even with the 13 pd hammer spring & already comes with ext firing pin and a cut down fire pin return spring. To many people blame "FTF" on the ammo maker. Be careful changing brands of ammo with the CZ customs or know that more than a couple of FTF's from any factory ammo in the same 500 rds are likely not bad ammo.

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I recently purchased both a JM pro and a Stoeger to use in my first 3gun. I got both of them because Im indecisive and would make up my mind after shooting each about which one to keep. I went to the LGS to pick them up and upon inspection the JM Pro had several nicks and scratches, a small bur or two around the ejection port. It appeared as if someone just dropped the gun on the floor and decided it looked good enough to put in a box and send it off. I can only imagine that if the outside of the receiver gets this kind of attention, or lack thereof, I wonder what the internals would be like. No wonder people are having issues. The Stoeger however was clean and evenly finished. It was also tagged with a Quality Control tag which was signed by an actual person. See ya later Mossberg.... never ever again.

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Some people have added the Nordic extended bolt release button to their JMPros. I did.

Note: the factory bolt release metal is VERY HARD. Even after chewing up several cobalt bits to finally make a hole, the tap that was included with the button was ground smooth by the metal, and a Ti-Ni tap I bought to replace it got chewed up similarly in short order.

The "trick" is to get it mounted in a vice, off the gun, and make the initial attempt at drilling with a perfectly parallel surface. I know that's basic shop 101 advice, but the shape of the button assembly makes it hard to get flat off a vice, and the knurling on the button becomes a bit-destroyer if you don't get the bit to bite perpendicular the first time. Coblat bits minimum, HSS isn't gonna cut it.

I ended up with an OS hole in the button, filled it with silver solder, then drilled and tapped that. HUGE PITA, but it's worth it if you have small hands. The button is more like a lever- works great.

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I recently purchased both a JM pro and a Stoeger to use in my first 3gun. I got both of them because Im indecisive and would make up my mind after shooting each about which one to keep. I went to the LGS to pick them up and upon inspection the JM Pro had several nicks and scratches, a small bur or two around the ejection port. It appeared as if someone just dropped the gun on the floor and decided it looked good enough to put in a box and send it off. I can only imagine that if the outside of the receiver gets this kind of attention, or lack thereof, I wonder what the internals would be like. No wonder people are having issues. The Stoeger however was clean and evenly finished. It was also tagged with a Quality Control tag which was signed by an actual person. See ya later Mossberg.... never ever again.

My Mossbergs have Signed QC papers by the person that test-fired it. I wouldn't really care if they didn't. Though I understand that few scratches may be a red flag to you, if you had the opportunity I think you should have stuck to your original plan and actually shot both to decide which works best for you.

You're going to find out in short order that 3gun makes your guns ugly if you're doing it right.

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I had issues when I first got my 930 JM Pro. Failure to feed, failure to eject, and bolt locking back. Talked to some shotgun gurus on another shotgun specific forum and was recommended that I "fit" my shotgun. After some back and forth with them asking me questions, they told me to install the drop spacer that came with my shotgun. Issues went away immediately, and have never come back. I have let a couple of friends use mine since installing the drop and they have the issues when firing it since it's fitted to me.

Check to see of your shotgun is fitted right, when quickly going from low ready to a firing position your head should naturally be lined up for you to look down the sights. If you have to adjust to head position when doing so, it's not "fitted" to you, and you need to experiment with the shims that came with the gun.

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I had issues when I first got my 930 JM Pro. Failure to feed, failure to eject, and bolt locking back. Talked to some shotgun gurus on another shotgun specific forum and was recommended that I "fit" my shotgun. After some back and forth with them asking me questions, they told me to install the drop spacer that came with my shotgun. Issues went away immediately, and have never come back. I have let a couple of friends use mine since installing the drop and they have the issues when firing it since it's fitted to me.

Check to see of your shotgun is fitted right, when quickly going from low ready to a firing position your head should naturally be lined up for you to look down the sights. If you have to adjust to head position when doing so, it's not "fitted" to you, and you need to experiment with the shims that came with the gun.

Personally, I would not be satisfied with the lack of reliability you describe. My JM930 functions in my hands and in the hands of friends, son, etc. I adjusted stock drop to correct poi to poa, not to fix a function issue. If I had a firearm that was only reliable after "fitting" I would look for the cause. Don't believe that is normal or acceptable. Its a tool that can cost points or life or limb, so needs to work under less than ideal circumstances. Just my opinion.

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The reason it was sent back before shooting it is because the dealer will accept a return "as new" for a full refund if the item is not transferred. The issue is not with cosmetics, I understand the firearm will not retain its "new" condition, but I just didn't expect that a manufacturer would send an item out in this condition. Maybe it was a great shooter, maybe not. I am more than happy with my decision. The Stoeger so far has performed flawlessly.

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I had issues when I first got my 930 JM Pro. Failure to feed, failure to eject, and bolt locking back. Talked to some shotgun gurus on another shotgun specific forum and was recommended that I "fit" my shotgun. After some back and forth with them asking me questions, they told me to install the drop spacer that came with my shotgun. Issues went away immediately, and have never come back. I have let a couple of friends use mine since installing the drop and they have the issues when firing it since it's fitted to me.

Check to see of your shotgun is fitted right, when quickly going from low ready to a firing position your head should naturally be lined up for you to look down the sights. If you have to adjust to head position when doing so, it's not "fitted" to you, and you need to experiment with the shims that came with the gun.

Personally, I would not be satisfied with the lack of reliability you describe. My JM930 functions in my hands and in the hands of friends, son, etc. I adjusted stock drop to correct poi to poa, not to fix a function issue. If I had a firearm that was only reliable after "fitting" I would look for the cause. Don't believe that is normal or acceptable. Its a tool that can cost points or life or limb, so needs to work under less than ideal circumstances. Just my opinion.

It didn't "fit" me because of the size of my chest and shoulders. It just didn't shoulder naturally. The toe of the stock was what would hit my shoulder when I would shoulder it quickly, and since it wasn't seated properly, it had the issues. Once I put in the drop spacer, it shouldered properly, and I had no more issues. It seems to only be an issue with bigger guys, and super skinny guys. I had the same issue with my old Stoeger, and a Remington that I shot that belonged to a friend. After having the same issues with more than one gun, I stated investigating to see if I was doing something wrong.

When my friends use it, the top of the stock hits them first. It just doesn't allow them to shoulder it properly without adjusting things.

I have another friend that is very muscular and he was having issues with his gun as well. His gun was a Benelli. I let him shoot mine with the spacer installed, and it shot great for him to. He added a spacer to his Benelli and his issues went away as well.

Edited by Tuflehundon
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I looked and when I'm logged in, there is not an "edit" button, only multiquote and quote? I don't know if my account is set up w/no ability to edit my own posts or why, maybe because I'm new? Any help would be appreciated, that way if I get new info I can just add to my orig topic/post. Tks

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Since I can't edit my orig post, I thought I'd clarify a few items:

Recoil/Cycling

-I only cut the recoil spring after about 250 rds of 1200-1250 fps rounds were thru the gun and all of the other work was done to improve reliability. I've read a few posts that claim you may be able to drill out one or both gas holes in the barrel to get more gas back to cycle slide for light loads ie...1100-1150 fps.

Stock LOP Shortened

-You will have to hollow out the hard plastic underside of the low profile limbsaver 5/8 inch thick pad about the diameter of a quarter to half dollar size and almost to the rubber (try to go just shy ). This is because when you cut off some of the recoil spring housing threads, alum spacer, and nut, you will still have the top of the tube & nut and just maybe 1/8 inch of one side alum spacer (maybe none) sticking above the stock as viewed from the side. It won't be below the stock. You might be able to get it flush, but not the plan with my pick. I also have the factory supplied spacer between the stock & receiver that angles the stock down a little to line up the rib so take this into account if you have nothing in between (1/8 inch maybe).

I'm going to try to shoot a few hundred of the lower velocity rounds next 2-3 weeks and see if they function (with the recoil spring cut minus 9 coils) and report back. I also will be shooting my first ever shotgun match at Pike Peak Shotgun Challenge. I don't expect much since I've only shot a shotgun ever since mid Feb, but I won't come in last for sure.

I did notice I shot a Rossi double barrel squire 26 or 28 inch barrel this year 12 ga I picked up cheap from a friend and I replaced the rock hard plastic butt pad w/limbsaver grind to fit and shortened the wooden stock before I ever shot it and it kicks no much worse than the mossberg 930 pro. Reason I'm writing this, is I haven't shot enough 12 ga autos to know, but I'm not so impressed with the mossberg shot to shot recoil control & muzzle jump, even before I cut the recoil spring w/1200-1250 fps bird loads. Just surprised how much jump it has with non magnum bird load stuff. Maybe I'm getting soft, I'm no tiny guy either, stocky (means decently fat and some muscle) and 275 pds to boot.

CZ Accu Shadow 100 yd group

-when I mentioned the 100 yd group was 7-7.5 inches. It was more like 8.5 inches with ultramax 115 gr. I used my outstretched hand & fingers at the range and they just fit between thumb & pinky and later measure and this is more like 8.5 inch group. Still good.

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I bought my 930 used from a shooter who won a Benelli at his first event. So when I got it it had 100 rounds thru it. I did nothing the first year plus and intentionally did not clean it to see how it handled it. Had 2 cases of where the carrier jammed against the receiver and one case where the extractor ripped the rim off a Win shell (switched to Fed and no issues). Finally cleaned it before last weekend's York 3man/3gun match. Also installed an RCI Xtention mag extension, spring, follower and +2 cap (12+1) even though I have never had a mag feed issue. Did it because one of my teammates just got a custom MKA1919 he wanted to shoot so we were in Open. Ran flawlessly. As for a shotgun sight I use the HiViz Triviz TT1001 ventrib shotgun sight set because the window or opening is bigger than the TruGlo (and you don't need any epoxy or anthing to make it stay on). As for AR optics I also use a Burris 1-4x24 MTAC. I find the BDC dots are dead on out to at least 300 yards using Walmart Fed .223 value packs. I like the reticle because it is like using a red dot at 1x (I don't turn on the light at all). In fact I took my Dueck offset irons off and put them in a box and have not used them since. Did put an offset red dot zeroed for 25 yards on for the 3m/3g match. Thinking about going to the MTAC 1.5-6x42 for longer range work although I am getting first shot hits at 300 with the 1-4x24. On one stage of the match you have to use another teammates rifle and none of us had an issue even though we had 3 different brands of scopes with different reticle styles shooting at steel from 75 to 175 yards.

Edited by photoracer
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Great info in this thread - I was seriously considering trading my 930 JM for a Versamax ..........

After trying some of the advice on this forum I'm probably going to stick w/ the 930.

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Friend of mine has had issues with his 930 ever since he got it. FTF, FTE. every issue you can think of. Took his and mine to the range last weekend and started swapping parts from mine to his to see if we could diagnose the issue. After taking it apart a couple of times, we left his side saddle off since it was a pain to take off and put on every time. As soon as he no longer had the side saddle on, his issues went away. He put the side saddle on before he ever shot it.

Not sure of the pins screws were a touch to small and it let the action move to much or what, but as soon as we put my stock pins into the gun it worked like a charm. The armorer at the range said he has seen several types of semi auto shotguns have issues once you install the side saddles. Only ones that didn't cause issues are the ones that Velcro on.

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  • 3 weeks later...

Well, I thought I had all the bugs worked out. The gun had 1 jam in about 200 rds with mostly Herters 2 3/4, 1 1/8 & 1 oz & estate competition loads and a few super target Win and Rem game/target 2 3/4, 1 1/8 oz, 7.5 shot and I haven't had any more or less problems with any brand loads from 1150 fps up to 1250 fps for about 200 rds. The last time out I tried some 1150 fps loads (50 rds) to see if the lighter loads would function and they did well (Remember in an earlier post it appears light loads have a hard time getting the bolt back enough to fully release the shell stop but spent shell ejects). I cut off about 9 coils on the recoil spring inside the stock. I also put in a Nordic tube spring and it's much stronger & thicker.

Now the past 2 times out I started having a lot of (appx 10% -25% out of 100) of the shell ejects but the next round never releases from the tube "unless I manually had rack the bolt, which works every time after this failure.

This problem the 2nd time out is now >25% of rounds shot. I had cleaned the gun pretty well including spraying out the entire receiver area & scrubbing the chrome removable piston & removed & cleaned the rings on the piston and there was enough oil in the gun so that during shooting the underside of trigger assy & rear receiver/stock joint leaks oil during shooting.

-I changed the Nordic spring back to the stock one, no help.

-Each time a shell doesn't release from the tube, a manual hand cycle of bolt work fine.

-I even tried some stout loads ie..heavy loads (hurts my arms, shoulder & cheekbone), no help, maybe worse

-I shot so many rounds of the hot stuff I had to hold it at waist level like on tv, trying loose & firmest grips even from shoulder, no help

-I checked the tube & spring/follower and it moves freely without snagging

-Happens during full tube, partial tube, and last couple of rounds

-Noticed regardless of hold some shells kick out far (6+ feet) and others kick out kinda weak (2-3 feet), even when holding firm shoulder, at hip level or loosely.

-Found no pieces, shell, metal or function blockers in, on, around any parts that I could see.

-Double checked the GG&G shell holder on the receiver and the screws and nuts were not tight or squeezing the bottom of receiver and the shell holder moves freely as well as the screws thru the trigger assy back & forth. The screws push thru receiver/trigger assy and screw into the GG&G and I put nuts on the other side of shell holder that have nylon locking in nut and they stay put.

I talked to Roger at Mossberg Tech Support 5/9/14 and he didn't seem to want to talk about any tech details but I told him I had to work out a lot of bugs but needed an extra shoulder stock recoil spring, shell holder tube spring, and shell stop assy including the shell stop pin & retainer clip and he was willing to send them to me for $45 shipped reg gnd mail. I'm at a loss as to what is causing the issue now.

I disassembled the entire gun and cleaned every part & orifice including scrubbing/scraping any buildup on piston/rings. I don't think cutting off 8% of the shoulder stock recoil spring should be causing this being there are 95-100 coils and I cut off 9 coils. The barrel gas holes didn't seemed blocked up, nor the piston very dirty.

Does anyone know if you are supposed to remove & scape/clean the items in the housing where the chrome piston slides into? Not the chrome piston & rings. It's the area attached to the underside of barrel just above the barrel gas port holes. Looks like a big wound metal item inside and has a metal O ring inside of that and has 2 slots on top as if designed for a slotted tool to remove it. I usually just use a wire toothbrush & solvent to brush it out thru top and bottom. Also should there be no oil applied to this section and chrome piston or light oil. I medium oiled it since new and just barely oiled it last time out after cleaning and no difference in fixing my function issue. Thoughts? It seems the bolt is not going back enough at times to fully operate the shell release during firing and works fine hand cycling after every round after the malfunction. Sometimes it's happening multiple shells in a row and then may fire 5 or 6 good then poof but I see no reason why. I will push something thru the barrel gas port holes to make sure they are not clogged and the gun will be fully cleaned next time out.

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Edited by AirForce2
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