Here's an interesting model that came out this year. I've always been curious about the S model, but never cared enough about short shells to spend the money. When Mossberg started selling them with a red dot cut, I couldn't resist. This is the model #51605. This is the basic model with 18.5" barrel. Stupidly it doesn't come threaded for choke tubes, so my barrel is away right now. Hopefully it will be back next week. The 940's come threaded for tubes already if you are looking at those.

I am comparing this to a basic model 590 with 20" barrel that I have had for a few years. I do not know the exact model number, but it looks just like #50694, except mine didn't come with a pistol grip. In all the pictures I tried to keep the 590s parts on the left, and 590 parts on the right.


Here are the internals side by side. 590s on left, 590 on right. I looked at them very close, and the only two parts that are different that I can see is the trigger group on the 590s has the rubber bumper on the front, and the shell lifter on the 590s has a slightly longer finger for lack of a better word. All the other parts look identical. I even swapped some in the other gun and they all seem to fit. It's pretty lame Mossberg doesn't sell the trigger group and shell lifter as a kit.







Here is the inside of the frames side by side. I can not identify one bit of difference at all. I see no reason you couldn't mill a standard Mossberg frame for a red dot, and that seems to be just what Mossberg did.







Here is the outside top of the frames. There's not much to see, but this 590s came with this metal and aggressive safety button that I really like. The one on the 590 is aftermarket, and what i usually use, but I see no reason to change out the 590s one. It is nice that Mossberg made the optic cut cover such that you an still use standard Mossberg rails and such.






Finally here is the optic cut. It is sold as an RMSc pattern, but you can see there are no recoil lugs. They are seemingly using the screw holes as lugs. They even sell some models ready to go with a Holosun 407k, so it will accept a K footprint optic with no mods. I'm still waiting for a red dot to show up, so I can't say much about it yet. I think it's a really nice idea that should put most of the red dot components below the frame surface, so all you see is window. The closer to the bore you get, the better suited for a shotgun it will be.








Some measurements

The depth of the optic cut at the front from the top of the frame to the bottom of the cut is .170" to .180" depending on the spot you measure.

The depth of the optic cut at the back from the top of the frame to the bottom of the cut is .130"

The length of the optic cut is about 1.620", but there is also a small cutout at the rear. If I include that cutout it is about 1.695".

The width of the cut is about .950".

The height of the "lugs" where the screws go into is .055".

The diameter of the "lugs" is .058"

The front of the optic cut to the front of the frame is 3.865"

I'm interested to hear from anyone else who has used the optic ready options from Mossberg. As I said, I'm waiting on both my barrel and a red dot to show up, so I have not tried it yet. As things often go, another option popped up as I was looking for one of these, and that is the Williams LRS. It is basically an upside down red dot, so all the stuff is on top, and the window is on the bottom. They aren't even priced bad, and while I really shouldn't have, I bought one. I plan to put that on the 20" 590 and I will hopefully be able to do some good side by side shooting.

It seems Defender Tactical keeps adding additional parts to their mini-shell adapter...
Now you need the lifter.

https://defendertactical.com/products/new-mini-pro-lifter-and-cartridge-arrestor-system-for-mossberg-shotguns

I tried the Opsol Mini-Shell adapter on my 590 Shockwave. It's annoying not being able to use more than 1 standard length shell - the chambered shell.

I picked up a 590S. I like the Ghost Ring Sights and how it's threaded for choke tubes.
Attached File


However there are times I miss having a shorter 18.5 in basic gun like yours.

That's one of the big reasons I never bought those adapters. Adapting to where it can ONLY shoot 1 3/4" shells is not for me. I'm really curious to see how the 590s does with 3" shells. I was playing with it some with 2 3/4", and the rubber bumper isn't even pushing on it, so I can't imagine it effects it at all. The 1 3/4" I could cycle as fast or slow as I wanted, upside down, left, right, I could not get it to hiccup at all. I'm quite impressed. The 3" do push against the rubber bumper, but I couldn't get it to fail to cycle. I'll have to try some actual shooting though.

It's really stupid how Mossberg is threading some 590 barrels for tubes, but not others. What would it add to the cost of the gun for them to do it and include a cylinder tube, $25? Now I have to send the barrel off for about $90 if you include shipping.

I agree yours should come threaded from the factory for Chokes. It just ultimately increases the use / effectiveness of a shotgun.

Seems Mossberg has no intention of making these parts available.  Sounds dumb to me, but hey, what do I know.  I'm hoping the trigger pack and elevator hit Brownell's or Midway soon, but I have a feeling they won't.

As an update, I still have not got the red dot I truly want, it is not in stock yet. I've been shooting it with a dirt cheap Sig RomeoZero that PSA had on sale for $70, and while the sights not that great, I really like the concept of such a low mounted red dot. I've got the barrel in full view which makes pointing very natural compared to a high mounted red dot with a dot floating in space.

I also bought a Williams LRS red dot and mounted it on my 20" 590. First of all the sight is not even made by Williams, it is 100% made in China. Says China on the box, even has a sticker on the sight that says China. The concept is really cool, but it needs some refinement. The emiter is way at the front, and if anything got in there it would be a real pain to clean out. The deal breaker for me is the performance of the unit. I asked the battery life and this is what I was told by Williams. There are 6 brightness settings

1-200,000 hours
2- 9,200 hours
3-2,500 hours
4-320 hours
5- 140 hours
6- 45 hours


1 is very dim. 2 is visible, maybe good on the range in some conditions. 3 I think is where most people would be. 4 is quite bright, but not horrible. 5 is very bright, probably not useful. 6 is crazy bright.

So basically it's a sight with a battery life for most people would last at best 100 days, could be as short as 2 weeks. That's not possible though, as this sight has no modes. It automatically turns off after 6 hours and that's that. No shake awake. You can't disable the feature. After 6 hours you have to push a button to turn it back on. Epic fail in my opinion. Even as a hunting sight, that's a fail.

Thankfully I bought from Amazon, and they are good with returns so I should get a full refund.

I'm sure it is on purpose.
They would never sell any of the complete guns if you could just get the couple parts needed to convert the older ones.
Why sell a couple parts they would only make a buck or two profit on, when they could sell a complete gun and make significantly more profit.

I bet eventually a company will make aftermarket versions of the needed parts if there is enough demand.

The biggest problem I see is ammo availability.
I pretty much never see short shells for sale anywhere.
Now if you could get mini shells at every store that sells regular shells and get them for about the same price, then yes, it would be worth it.
But until then, I will stick with normal shells.