mpom
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Posts posted by mpom
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RAS stands for Rose Actions Sports. Steve Rose is the guy, goes by Gun Cat. No personal experience, but seems very willing to share his knowledge of shotguns, from reading his posts. Probably more likely to be of help than Mossberg, and a phone call is cheaper than shipping, which is always an option after the call!
Feel bad for you, as I would be pretty pissed, having put in the work you did, and then having frequent malfunctions.
Can see why people have been washing their hands of JM930s of late.
Hope you get it straightened out soon, whether its the gas system or shell release, or something else.
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Fortunately have not had to analyze this portion of the 930, but would bet that Steve at RAS is familiar with it! Seems very willing to share info in the forums. If I had this issue, I would call him up. 270-348-3262
After all, the brain trust here is not getting it done ;-)
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FWIW, with the +2 cap, running full length factory mag spring.
Sorry i don't have enough experience to offer any help...
Why not call up Steve @ RAS? Doubt he would mind and you have nothing to lose.
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Probably did not explain myself clearly.
I left the face contacting the shell rim flat, but cut a radius in the "vertical" edge, to mimic the radius in the shell rim, so when shell stop moves aside in order to release a shell, contact is lost all at once. Just took out a bit of the center of the vertical edge with a 1/2" round drum in my dremel.
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No expert here, but have you cleaned up the front of the shell stop? the piece that stops a shell from coming onto the lifter? Someone mentioned that it should have a semicircular shape, with the edge towards the center of the mag tube reshaped like a crescent. mine was a straight edge and the recommendation was to cut the middle away, so the shell rim is released with a bit less movement of the shell stop needed. Polishing the front and back of the front end of the shell stop helps make mine easier to load as well.
No harm in doing this mod, as long as you dont remove too much material from vertical edge of front of shell stop, to the point shells pop out of mag tube before they are supposed to.
maybe The Man from RAS has an insight into your problem.
Tito, never shot 7/8 oz shotshells, so dont know if they work, however 7/8 oz slugs are 100% in my 930JM. Not sure if there is a velocity difference.
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Sounds like the round is being directed towards the ejection port rather than the chamber, by the shell lifter. If you have dummy shells, I would observe the way shells are handled by the lifter. By tweaking, I assume you bent the lifter into better alignment. Also, the sharp right edge at the chamber opening, by the extractor, can interfere with reliable chambering. Easy to fix, along with the sharp edge at the top of chamber.
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I think a major issue with the JM930 is not the design, as many including mine, run great, with NO malfunctions per match, but with Mossberg's quality control. They seem to leave a lot of sharp edges, have rough machining, weak springs, etc, so while economical, many folks do have reliability issues. If Mossberg put a little time into tightening tolerances, reviewing spring specs and assessing what their vendors are supplying, plus polishing working surfaces, they would have a more consistently reliable shotgun, although more expensive to produce. So they leave the detail work to the end buyer, which I can live with. As long as a buyer knows this, I don't think its a bad deal.
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As far as carbon, been using FireClean for lube and while carbon does not just fall off, it is not hard to clean with brass tooth brush looking brush. Only clean gas system every 3-400 shells.
AF2, have you checked for free motion of piston with the handguard off? Similar to what JM shows in the video, but with the barrel on the frame. Just wondering if there is any interference between the piston and mag tube. Sounds like your SG works with higher powered loads but not with lower powered ones, so wonder if there is excess friction somewhere hampering function.
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Thanks to Oskino and others, I took the plunge and went dremeling on my perfectly fine JM930. Did not do the sides, just the front end where my thumb ends up. Also reshaped the ass end of the handguard to look and function better, if I get into deuces and quads in the future. Finally, stippled the grip- a major improvement when reloading as it feels much more secure with only one hand on the gun.
Lifter work by CRums. Sorry for the crappy phone pics. -
If wearing out the firing pin bothers you, then a solution (other than a spare fp) is: http://www.midwayusa.com/product/872223/tma-ar-15-dry-fire-device-delrin-orange
Prevents hammer contact with fp and reduces the amount of retraction required to recock hammer. Pretty neat, just drop into bolt carrier, done.
Just don't forget to take it out before firing or it goes click instead of bang. Don't ask how I know...
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Did the Nordic follower as well, and ended up losing a round capacity, as mentioned above. So cut off around a half inch of back section, smoothed and beveled, so back to 9+1, no hangups.
+1 on polishing mag tube where piston lives, as it makes cleaning much easier.
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Ranier Arms has a variety of lowers, including some branded for them, which are of very good quality.
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As far as cleaning, maybe every few hundred shells.
Suspect reason for follower hanging up is poor match at the junction of the mag tube screwed in to receiver and the Nordic extension where they screw together. If you take out spring and follower and shine a light down from receiver while looking down tube from front (MUST make sure firearm is unloaded first, not that anyone on this forum would not) you will see the fixed part of the mag tube. Edge is probably pretty sharp and can catch the follower. Try dropping it down a few times. If so, then you can file and polish or dremel the offending sharp edge so you end up with a smooth transition and no hangup of follower. Reason its not an issue when live firing is probably because of all the recoil and inertia of shells during live fire.
Would suggest a complete teardown, cleaning and fluff and buff, since the gun is pretty new. The gas piston and tube it rides on (mag tube) often come with grease/grunge from the factory, no extra charge.
Search the SG forum for lots of info on the JM930. Glad yours is functioning well as they have a mixed history. Took some work, but mine runs well also.
A good summary thread: http://www.brianenos.com/forums/index.php?showtopic=192975
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Thanks, I'll try going back to the original mag cap, run it and see if that solves the problem. Anyway, a nordic components replacement spring is on its way. Should I cut that to 14" past tube end too, or 15.5" past to account for XXL cap?
FWIW, some folks recommend buying 2 springs, so if one is cut in stages, and ends up too short... Since you presumably only have one coming, I would tend to be conservative and maybe run it longer than necessary, since you cannot experiment to find the lower limit. With my XXL cap, its reliable at 10" beyond end of tube with cap off, but am running the original spring as its easier to load. Got the Nordic as a backup. Better safe then sorry.
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Nice to hear.
Had a somewhat dinged up choke tube in the set when I opened the bag they came in, when I received the new shotgun. Called up CS and they shipped a complete set of chokes.
Good to hear not all experiences with Mossberg CS is bad...
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Stippled the front of the grip, pretty aggressively with overlapping medium sized "dots". Feels great holding the shotgun one handed. Have not fired it since stippling. Tried the tape first, but could not get it to lay flat due to multiple curves in grip. Took a chance with permanent alteration, but like it. Am considering doing the sides of foregrip, but not sure it would help. Does it?
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You mentioned rounds 1-8 feed fine, so its rounds 9 and 10 that missfeed?. Sounds like it might be mag tube spring tension that is the culpirt. Why not replace the XXL cap with original cap and see if problem is resolved.
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http://www.carbonarms.us/AR-15-Uppers-and-Parts/Dynamic-Resistance-Muzzle-Brakes.html
Main claim to fame is light weight and short length, along with low blast, while still providing excellent function. Believe there is a thread with positive feedback on this forum, which led me to get one. I like it.
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Tuflehundon,
Learned something, thanks.
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What, no love for the Dynamic Resistance comp?
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Second the Inforce WML; very light and low profile, and super bright. Changed out my TLR and don't regret it. At least 3 versions I know of; momentary only, programmable and one with IR illum, for NODs.
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Kick eeze has a series of comb pads available via brownells, from 1/16" and up, that might help the face/cheek slap.
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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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mwc5, I would look at pictures of the 930 fire control group/trigger housing available on the net and compare to yours. My bet is that it was reassembled incorrectly.
Fact that there is no firing pin mark on the primers when you attempt to fire, yet hammer drops, leads me to think its not a weak spring problem, but a mechanical problem, probably blocking the hammer from contacting firing pin. Something is where it does not belong.
Might be worth the cost of a visit to a local gunsmith that is familiar with the 930, if that is an option. Where are you located?
DIY Loading port work and welded lifter
in Shotgun - Technical
Posted
http://imgur.com/qhEbyqL,amnDo7Y,ZjHOYj5#0
Hopefully the 3 photos will show up!