Mossberg 930 JM Loading Port

[gng4life]

If anyone is interested in trying this modification at home, I documented my process as a tutorial. You can see it below. Total time spent was about 2 hours from strip down to reassembly.

Looks good! Thanks for sharing! I posted a comment on your YouTube video also.

[two shoes]

So I have a new JM 930 that Mossberg replaced. I had some gouging on the mag tube and when I called them, they said it was normal. I let them know that Stainless steel should not gouge like that... they said send it in. I got back a different gun (serno) so that may have been quicker for them than to look it over, no problem. Well seeing all of the coolness here and wanting to be part of the "in" crowd for the first time in my life, I decided to open the port a little.

As a recent graduate of WECSOGS, I felt empowered to do this. Just after I started with my professional tools, my 15 y.o. boy sees me with a file in my hand.... The following conversation was had:

him - "Hey Dad, what are you doing?"

me - "Opening up the loading port on this shotgun, I want to be one of the cool kids"

him - "Uh, is that the one you just got back?"

me - "yep"

him - "We haven't taken it to the range yet, right?"

me - "yep"

him - "Does Mom know you are doing this to a new gun?"

me - "nope!, let's keep it that way..."

him - "I can't believe it! You're crazy Dad!... Will I get to shoot it?"

me - "Of course"

I don't have any "before" pics, but most of you know what they look like.

Benny Hill has said a couple of times to undercut it. I have never met the guy but he seems to be "popular" around here so I did work on it from that direction, although it doesn't show up very well. Very, very smooth... Will post pics of my tools later... Let me know what you think...

Now, to get a welder lifted....

[mpom]

How hard was it to remove the mag tube?

mark

[two shoes]

I did it by hand, not in a press. The only mechanical advantage I had was 8" 2x2 and a tight grip on the mag tube. Slow, but steady...

[bigkyle72]

What is that little pin on the port? I was going to open the port but didnt know what that little pin was and how much i could mill away and if it would effect it.

[BobS761]

What is that little pin on the port? I was going to open the port but didnt know what that little pin was and how much i could mill away and if it would effect it.

That pin holds the shell stop/catch. You don't need to get into it to open the port enough.

[Nickoli]

Ok guys, I am not sure if the newer ones are the same as the older ones or not. I have been working on my port since I got it and just set it up for quads.

I wanted to open up the front of the port more so more of it was opened past the shell catch but the mag tube is right there and I was not sure if I should cut into that or not with the threads being there as well. I will try and take pictures tonight and see if I can load them up or not to try and make things easier to explain.

[dhill]

Be careful that you dont cut away the follower retaining ring. If you are seeing the tube and threads you are probably going too far.

[Nickoli]

Maybe I was thinking my follower was tucked in more than I thought...

Here are the pics I took tonight, the follower is out a little bit. Shells stick out this far as well. I was wondering how likestoshoot opened his port up because right now,.if I go any further forward I'm going to cut into.the mag tube and threads for it. I have it right at the edge of the tube now even though you can't see it if the pictures.

On another note, how does everyone else's hand guards fit? I have been trying to figure out a way to get mine to hug the receiver because as it sits now there is about 1/8" gap between the hand guard and the first piece that goes on over the mag tube, not sure what its called. I have had problems of shells catching this gap when loading quads and I'm wondering if anyone else has this problem.

Edited November 2, 2013 by Nickoli

[LikesToShoot]

Nick,

Yours looks really nice. I went ahead and cut into the steel tube, just make sure it's tight in the receiver. Try to find Mark's link for loading port mods, VERY good info from a generous man. You'll find that an undercut, taper on the inside of the receiver, will really help funnel the second shell in.

I can't help with the quad and fore grip, that's my winter practice once I get a quad set-up.

You might want to search you tube for the shell catch take down video. De-horning that potato peeling catch should smooth loading and keep the trigger group and catch / bolt release cleaner.

[Nickoli]

Thanks, i have polished the shell catch did the double feed prevention, and since reading on the VM mod for the catch I will be doing something similar this winter along with making other things such as an extended bolt release.

You can't really tell in the pictures but the reason the right side of the receiver looks wider is because of how far I cut up the receiver. You can see it a little bit in the first picture. I did this for the purpose of quads. My thumb would be forced on the other side of the receiver they way I had it opened before similar to yours.

I read over Mark's write up, I wish it only took me 90 minutes to do that. I have a couple hours invested with the amount of times I have changed it slightly.

When you cut into the mag tube did you leave it screwed into the receiver or did you take it out, cut the receiver and then thread it back in to see where you needed to remove material like Mark showed?

[LikesToShoot]

I cut it as installed, that way it's formed right to the receiver cut and smoothed out with same.

It might no be the right way to do it but it works. Over time it has started to back out and I have to tighten it up to keep the steel lip from covering the relief cut in the receiver.

Are you strong hand loading quads?

Edited November 2, 2013 by LikesToShoot

[Nickoli]

Yes, I just started to practice with it a month or so ago and shot 1 match so far. I tried weak hand quads but it didn't work out so well.

[Shrek926]

Great information, and photos everyone! My 930 is a bone stocker... But not for long.

[zachvu]

Thanks for all the info! I'm running a Nova (part of the "out" crowd) but liked seeing the port options/methods!

[LikesToShoot]

Thanks for all the info! I'm running a Nova (part of the "out" crowd) but liked seeing the port options/methods!

Here's something I think you will really like:

http://www.brianenos.com/forums/index.php?showtopic=166311

[ScoutRecon]

Here is the one PT did based on what James and I had previously done. Notice that a lot of effort was put into making the transition out of the loading port smooth so that the "pet" motion can be used. Not the best angle for it, but look at the thickness of the black on the upper edge between the port mod and the side. Notice the angle. It is smoother and faster this way.

MarkCO, can you give me a walk thru on how you filled the forearm w epoxy? I shaved mine down and now with the gap the 930 creates its super sharp. During dropping dueces, it cuts up my hand and im trying to find a solution. Thx

[3gunNoob]

My buddy just opened up the follower area. This is going to greatly improve stuffing in shells for quad load. Notice how much shell is exposed.

 

my question is does c-runs also extend the lifter or is that necessary? There is more space between the follower and lifter now than there was before. I have looked at many many port mods and I never felt that the follower was exposed enough. Not lite this one.

[LikesToShoot]

He can try loading without having the lifter extended but most people end up getting their thumb pinched by the lifter. 

[3gunNoob]

I’ve been lucky about pinching. The reason I wanted the cut around the mag tube are more aggressive is so the shells latch into tube much easier without needed to stick my thumb in there. I just thought that the lifter being a little longer would also aid my thumb sweeping the rounds into tube.

 

by the way I see that Jerry Miculek has a website that offers an after market lifter also. 

[3gunNoob]

Hey LikesTo Shoot,

What do you use for shotgun and who mod’Ed yours. I’m just trying to get more matches with JM. But I am going to move up to VM competition. 1) The loading port, when properly modified looks extremely better for quads, 2)my neck needs a soft gas gun and VM Is the softest.

[LikesToShoot]

On 10/2/2019 at 11:22 PM, 3gunNoob said:

Hey LikesTo Shoot,

What do you use for shotgun and who mod’Ed yours. I’m just trying to get more matches with JM. But I am going to move up to VM competition. 1) The loading port, when properly modified looks extremely better for quads, 2)my neck needs a soft gas gun and VM Is the softest.

Still using the JM, if you keep it clean it works fine. (Until you bump the bolt release with a round chambered and the gun locks up until you pocket knife the shell back into the tube, big design flaw). Always carry a pocket knife!! 

I picked up a barely used VM because that JM design flaw screwed me a few times and I “Knew the VM was Better” Haha on me.  

I’m still trying to get the VM sorted out. 

1st, I couldn’t hit s#*t with the VM, apparently some barrels aren’t straight. Fixed that with a rear sight and now can used slug out to 100 yards and score 21-24 often shooting trap.

2nd, VM extractor wasn’t working well so I  installed a Benelli one and that’s fine now. Imagine having to extract shells during a stage with clays flung in the air.

3rd, extra weight of extended lifter caused issues. YouTube was big help there.

I’m back to using JM when I have time to play ( not much time this year) because I can count on it until I get more time with the VM.

I recommend you get used to the JM and the game, save your money and skip the VM.

[3gunNoob]

Hey Likes to shoot.

i know when you hit the bolt release it lets the next shell from the mag tube. I actually  like that feature when I’m practicing quadloads. I hit button, get round and put it right back into my caddie x8. Now that you told me what happens if I hit it with a chambered round, I’m gonna be spooked. So I guess the round comes out of tube and gets caught above the lifter. Can you just pull charging handle to remove chambered round and then on forward movement of bolt loads the round sitting above the lifter???

im guessing that won’t clear the problem because I read your posts and you know your stuff.

[3gunNoob]

But anyways, as far as keeping it clean, I have observed people who actually buy the gun and just go out and shoot it without cleaning the large amount of grease in all parts of the shotgun. I’m convinced that these are the people who then make entries in the forums about all the failures. I have never dealt with any failures with 1000s of birdshot 7.5 and keep the dram at 3. I have had a couple of failures this year with Remington slugger 1600 FPS. But I just rack the gun and next round runs fine and doesn’t repeat the failure. It happened on jungle run stage. 

 

I need to to fiddle with various slugs to see what it likes. Could anybody out there give advise please? 

 

Also, LikesToShoot,  I have just contacted Jeff from c-rums and ordered the extended welded lifter. Can’t wait to try that out. I’m giving the jm pro a 2nd mod and lifter as a continued usage of the gun till the timing is right (wife) to buy the Remington VM Comp. I was at the gun store today and held some Turkish duck gun that had a 3.5 inch chamber and WOW. Can you give me a rundown of problems with VM. I thought the barrel not being straight was just typical forums BS.

 

Also, what  rear sight do you use for JM Pro. I have been running it with just the front for a year and was enjoying how quick and easy I acquired my sight picture.

 

well that was a lot of typing, hope you take the time to help a fellow competitor out.