Mossberg 930 design question

[Dustysa4]

I'm somewhat new to this board and to competitive shooting. I've spent about the last week looking at long threads on here and mossbergowners.com, reading about 930's having trouble feeding from extended magazines. I recently attached the Nordic +5 MXT extension to my 28" field model, and began having this issue. I have taken everything down to bolts, polished the shell stop, and still have the issue. I was assuming/hoping that it was a combination of spring pressure against a rough shell stop, so I trimmed the spring as well, one coil at a time, and at this point I'll probably need a new spring. I'm at 5" past the end of the tube and it still won't feed the 1st few rounds from the tube on to the lifter. I'm sure this problem is old news for many of you...

My question is whether this issue is actually even an issue? When I refer to my manual it states that the proper way to load the 930 is to drop a round in the side port, drop the bolt, and then fill the magazine tube to capacity. Is the recoil of the round loaded in the chamber a designed & timed element, allowing a momentary shift of pressure off the shell stop, and thus allowing everything to function? I haven't had a chance to test this theory yet, but I'm curious what others with this feeding issue have noticed. If that's the intended design, cruiser ready becomes more tedious. Thoughts?

[Nuke8401]

So it sounds like you only have the problem when hand cycling vice shooting the gun? I would guess/bet that if your gun loads fine when shooting then it will load when hand cycling if you how should I say, cycle it like a man? Just kidding, but really if you cycle it aggressively I think the mechanical shock of shooting the gun can be duplicated enough to make it load from a full mag tube. I will try to post a link when I find it.

Found it, dang almost 2 years ago now.

http://www.brianenos.com/forums/index.php?showtopic=142693

It can be important to be able to hand cycle rounds for empty chamber starts so figuring out how to make your gun hand cycle/load is in my view important.

Edited October 10, 2013 by Nuke8401

[Dustysa4]

Thanks for the response Nuke. Yes, your assumption is correct that it's not feeding from the magazine when HAND cycling, and only with the extension kit installed. Believe me, I've just about ripped my finger off, really cycling it as quickly and forcefully as I can, with no success. I've been sure not to "short stroke" it as well. Without the extension, rounds move past the shell stop with minimal effort. I also agree with you, if the shotgun was not designed to be loaded using the charging handle and the bolt release button, it no longer serves the purpose I bought it for. Even if it worked 50% of the time, that's not going to cut it for gaming.

Edit: I've actually seen that thread via search and have performed the things you mentioned. It seemed to help some. Still not to where I'd use it in a match. Thanks for your help.

Edited October 10, 2013 by Dustysa4

[wgj3]

From your initial post, it almost sounds like the action of retracting the bolt isn't moving the shell stop enough to allow a round out of the magazine tube. But, it doesn't make sense to me that you would only see the issue with the extension in place. Also, I think that more spring in mag tube is better than less for functioning. (Less spring for capacity.)

If you load the tube with the extension installed and flip the gun upside down then push the lifter down and manually depress the shell stop, does it squirt a round out of the tube into your hand, etc.?

I ask because it seems more likely that the rounds are getting hung up in the tube from gunk or misshapen follower or bad junction between integral tube and extension or something like that. Im certainly not a pro, but I have a 930 that usually works.

Edited October 10, 2013 by wgj3

[lc2hl]

I found a light burr / dent on the end of the factory mag tube on one of mine. Check to see that there are no hangups there. A slight dimple there will cause exactly what you are describing. After using a ball peen hammer to "round" out the end of the tube, both of mine have fed flawlessly.

During shot/recoil there is enough movement to feed a shell, but you are only relying on cycling a bolt to feed by hand, which is less stress on the feeding system.

[usmc1094]

My 930 JM doesn't have this problem but you could try pushing the bolt release (on a closed bolt) should put a round on the lifter. But that's not really fixing the problem just going around it.

[outerlimits]

it is not designed to work that way. there are ways around it, lot's of tinkering and i got mine to work.

[toothandnail]

My son and I both have one , extended tube, never had any problems whatsoever.

[Dustysa4]

wgj3: I can literally rapid fire shells out of the loading port by doing the manual unload you described. There is definitely pressure against the shell stop.

I had a chance to look at my friends 930 Rhythm. He has the same dummy rounds I do, so we loaded it up with 13 in the tube (!&$! Awesome!) and it hand cycled rounds 13 through 1 with minimal effort. I walked it back as slowly as possible and once the bolt carrier moved back past the rear shell stop tab, the whole shell stop assembly would pivot, the front stop moved out of the way, and the round popped out of the tube and on to the lifter. I went through his dummy ammo and found the most chewed up examples and they all performed flawlessly.

He was kind enough to let me take it down and examine everything. The differences I found (other than the obvious blue furniture and +9 extension tube):

His mag spring extended almost 2' past the end of the extension, it was never trimmed.

His mag spring is "finished" on the follower end, as most factory springs are.

His mag spring uses a thinner gauge.

I suspect his rear shell stop spring might be a heavier spring too, but it's hard to tell. This weekend I'm hoping to have time to swap parts and see if his mag spring and/or rear shell stop spring will allow mine to function. Thanks for all the replies and suggestions. I really do appreciate it.

Edited October 11, 2013 by Dustysa4

[LikesToShoot]

Mine used to have problems not releasing a round when I hand cycled it. This started after many rounds of use but worked OK when live fired. I had noticed that the shell stop was shaving hulls and clippings were getting into the trigger group and behind the shell / bolt stop area. After I cleaned the peels out it worked fine until they got clogged up again. Since then I've reshaped and dehorned the shell stop, no peels and no problems.

How many rounds are thru your gun?

[Dustysa4]

LikeToShoot: It only has about 250 rounds through it.

The good news is that I was able to compare side-by-side with a Rhythm that functions as it should. Simply swapping the +9 tube and un-trimmed spring on to my 930 made it function properly. I went ahead and pulled them completely apart and everything seems to be identical otherwise, less the blue furniture. I was surprised to see that the shell stops were identical (Mossberg says the Signature Series has an over-sized bolt drop button).

The un-trimmed Rhythm spring on the left, my factory 4+1 spring in center, and the Nordic spring on the right. Also note they are arranged from higher gauge (left) to lower gauge (right), and that the Rhythm spring uses an obviously different coil rate. I believe that while Mossberg sources Signature Series extension tubes from Nordic, it seems they use their own spring. Why some people have no issues using the Nordic Components spring, and others have issues, is beyond me. I'm just happy I *think* I found a fix...

Edited October 13, 2013 by Dustysa4

[Dustysa4]

Final update for future searchers with the same issue...

I called up Mossberg and ordered a pair of their 10-shot JM Pro mag springs. The CS person on the phone indicated that the different models of 930's had different springs, but the shipping invoice I received says SPX, so...??? I installed the spring and now it hand cycles like it should. The spring required no trimming, has a lot of excess past the tube, and is finished nicely at both ends. At $3.50 each, might as well buy a few since it is a wear item.