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LonesomeDuck

To JM Pro or not to JM Pro........

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On 4/8/2018 at 1:41 PM, LonesomeDuck said:

Yep,  I almost ordered all of the goodies in their blue competition package last week.  I'm going to call them back in fact. Those folks run nothing but Mossberg.  I'll see if I can get anything difinitive.  Maybe they will reveal the great mystery of Jerry.   Do I need to avoid a certain window of fabrication?    Hopefully they will say something like,   "it's easy,  avoid the models produced in Connecticut during 2014,  our foreman was blind and he fell into the foundry one day and no one noticed.  So we had a bad batch of steel that year."......   

 

Unfortunately it isn't quite that easy. 

 

Some of the early issues with the 930 were user induced. The SPX was by far the most popular model and nearly everyone added a side-saddle that replaced the trigger pins with a bolt  that tightened the receiver up to the trigger group. This would often bind them up into regular malfunction or worse turn them into single-shots as varied levels of torque was applied to an assembly that was supposed to have play in it to keep the receiver the proper factory width. Some speedloader brackets were too tight and did the same thing. This and a bunch of barrels leaving the factory with canted sights set the early reputation of the 930 to less than reliable. The Choate magazine tube extension on the SPX was (and still is) also problematic. They properly used a Nordic on the JM Pro. You can make it worse again by placing a sling bracket between the forearm and magazine extension. The factory follower won't make the jump reliably with one of these installed.

 

The sensitivity of gas system components to dew point and humidity Issues are well documented and addressed by the MST.

 

Issues of general quality control are there, but are typically small things that are easy to address if caught early. That said, they turn into big things if they aren't.

 

Spring burrs that can be fixed with 5 minutes and a Dremel will otherwise start to eat the return spring plunger after a few hundred rounds. It doesn't become a big deal until it starts to score up the interior of the return spring tube and drag the recoil system down. Likewise, a burr on the secondary gas system spring can score the magazine tube and cause the gas system to leak if not addressed quickly. The JM Pro's magazine tube is tougher and less likely to get scored by the spring. These spring burr issues both show signs early and can be avoided completely by breaking the gun down when you get it and giving it the quality control it didn't get.

 

Some guns escaped the factory with rough chambers. Cheap, thin hulled shells that sometimes lock up pumps will hang up in these chambers as well. 2 minutes worth of polishing with the correct materials and the problem is taken care of.

 

Some of them have feed from the tube issues. Brownell's addressed this one years ago in a DIY tutorial:

 

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=15831

 

The rest comes down to how you make it work specifically for your purposes. They will run loads lighter than many shotguns ever dreamed of with the right parts. They won't do it from the factory because they are designed to survive 3" magnums and springs are supplied appropriately.

 

They can be more difficult in theory to quad load, but in reality the magazine tube is set pretty shallow into the receiver compared to many other guns. The forearm overhang is easy to deal with and most people open the loading port up anyway. You will want to either open up the end of the lifter and open the port a bit forward to keep your thumb.

 

If Mossberg spent a few minutes extra with each gun in assembly line form they would be a lot more consistent out of the box and the only things that would need changed would be done for specific usage. Tearing one down and doing it all to a single gun when it shows up takes about an hour and $75 worth of parts to make it run as reliably as anything out there until it is time to clean it. You WILL have to clean it.

 

 

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Excellent post, Logis    :bow:

 

Extremely valuable - instead of just complaining that the JM is unreliable, you

broke it down very simply, yet thoroughly ...

 

Wish I were "handy" enough to make all those changes to a JM    ....    :( 

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I recently found some Benelli M2 Americans on GB for 699 plus 20 shipping.  The one I saw was in camo and 26" only.  Not the perfect gun...but I think it's a much better value.  Might research if it's possible to remove the hydro dip from it if you prefer a black gun.  I plan on picking one up for a strictly hunting gun.  They do not have the ComforTech stock and only have one choke.  Most likely you will replace the chokes anyhow with extended versions.  You can add a SIMS recoil pad for a little extra and have one heck of a gun.  I'd say for a total of $1000 you could make it into a wicked 3-gun shotty.

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Posted (edited)
On 4/10/2018 at 7:48 PM, logiztix said:

 

The rest comes down to how you make it work specifically for your purposes. They will run loads lighter than many shotguns ever dreamed of with the right parts. They won't do it from the factory because they are designed to survive 3" magnums and springs are supplied appropriately.

 

They can be more difficult in theory to quad load, but in reality the magazine tube is set pretty shallow into the receiver compared to many other guns. The forearm overhang is easy to deal with and most people open the loading port up anyway. You will want to either open up the end of the lifter and open the port a bit forward to keep your thumb.

 

If Mossberg spent a few minutes extra with each gun in assembly line form they would be a lot more consistent out of the box and the only things that would need changed would be done for specific usage. Tearing one down and doing it all to a single gun when it shows up takes about an hour and $75 worth of parts to make it run as reliably as anything out there until it is time to clean it. You WILL have to clean it.

Bumping, as I was checking in after loong absence.  I'm not a competition shooter, but stay here for info for high-volume, hard-usage on  various platforms.  I bought 2 930 SPXs a few years ago.  Mine are training/home guns, and have about 1500 rounds, mixed, through each of them.  Not much, but more than the average hobbyist. I switched the stock mag tube for the stainless 9200 tubes (before you could buy the JM tubes), and used a brake hone to polish inside the tubes & chamfer the throats.  I was able to get the chromed gas pistons.  Also honed & chamfered the Choate extensions, as well as the mainspring tube (using 3M pads & polishing compound).  Added OR3Gun goodies, and a velcro side saddle and commenced to burn through a case. Definitely not a "picky eater."

 

They have some quirks, but definitely run

Quote
Quote

 

 

 

 

Edited by Rob72

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Lena's Mossberg broke at World Shoot and she had to move to a backup...  This is at least the second time I've heard of this for her.  Never heard of someone having to go to a backup Benelli.

 

She's so good that she still won, but why would you want a gun that always has a pretty decent risk of breaking.

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13 minutes ago, bluedevil008 said:

  why would you want a gun that always has a pretty decent risk of breaking.

 

If they gave them to you for free, maintained them and paid me  $$$$.    :wub:

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Excellent analysis !!!      :cheers:

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Mine has run everything I put thought it for 4 years. Must make sure the piston rings are clean.

 

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Everything huh. Congrats. You’ve got the only one 

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Posted (edited)
On 6/12/2018 at 12:44 PM, Nathanb said:

Everything huh. Congrats. You’ve got the only one 

Not the only one. Mine functions w super light loads as well as with conventional loads. Did take a fair amount of tweaking springs, parts polishing and a few parts from Logiztix. Hopefully will remain reliable for a long time but who knows.

Definitely a gun that needs some going over to make it reliable, so if one does not want to invest some time and money perhaps something like a Beretta 1301 is a better choice, at a higher price point.

Edited by mpom
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20 minutes ago, mpom said:

Not the only one. Mine functions w super light loads as well as with conventional loads. Did take a fair amount of tweaking springs, parts polishing and a few parts from Logiztix. Hopefully will remain reliable for a long time but who knows.

Definitely a gun that needs some going over to make it reliable, so if one does not want to invest some time and money perhaps something like a Beretta 1301 is a better choice, at a higher price point.

 

Just out of curiosity, how much money in parts/tuning do you have into the JM?

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Around $50, not including having the shell lifter welded up, something most SGs need to avoid bloody thumbs.

Mark

 

 

 

 

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Also not the only one. I use Walmart bulk Winchester and shoots every time, as long I keep it clean. Been shooting for 4 years. Dad opend the port and C-Rum welded the lifter

 

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Mine has at least 7000 rounds through it and as long as you keep it super clean it works great. I completely take it apart every 350 rounds.  Although I did have issues with light strikes in the cold weather but I put in a Ruger 10/22 extra power hammer spring. It was a direct fit and has run smooth for the last 2 years

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My Flannigan has run like a top for 5 or 6 years. Idk if they did things different on those guns or if I got lucky, but it hasn’t given me any trouble so far. 

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had the JM pro for the year, put the money into it, sold it, going for benellii now. at ran 95% of the time, that other 5 though..... UGGGHHHH'

 

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I have a friend that shoots one and competes all over the country.  It is not a bad shotgun.  If you beat on it hard small parts break.  However with the Or3gun spacer, and recoil system, and an SBE Precision competition piston his has been running like a beast.  He ran 2000 shells last time with no cleaning and zero malfunctions.  It is possible to get these to run really well.  The base gun isn't quite ready for prime time, but with a little work it really runs well.

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On 8/4/2018 at 4:58 AM, Spencerb1911 said:

Mine has at least 7000 rounds through it and as long as you keep it super clean it works great. I completely take it apart every 350 rounds.  Although I did have issues with light strikes in the cold weather but I put in a Ruger 10/22 extra power hammer spring. It was a direct fit and has run smooth for the last 2 years

 

My friend has the new SBE Precision Products stainless steel piston.  It uses only the outer ring, and has gas grooves on the inside.  He went 2000 shells without cleaning or any malfunctions.  he also uses the Or3gun recoil system and marine spacer.

 

This is 2000 shells worth of fouling

 

IMG_2950.jpg

 

 

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Don’t go the cheap route or you will be buying a new gun in less than a year.

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