After seeing a couple of pictures of 870's with the old military bayonet lug I decided I needed one too but quickly realized they are very hard to find, very hard. Then I found this EvilBay auction Is this how much they are actually worth? Ouch. I could almost buy a new 870 for that price. Guess I don't need one that bad after all.

There are people on Ebay paying $150.00 for FAKE Colt Python grips, so Yes, the military bayonet mount is selling for that price.

In fact, the actual selling price is usually HIGHER then the $200.00 price on this one.

G.M. Chrysler......$200?  You could buy an entire 870 for that or some high speed stuff from mesa or wilson. Me thinks my shotty won't be getting a pig sticker anytime soon.

Any other sources out there for this item?  I'd like one if possible.

No one ever made a commercial version.

Those are pretty rare thats why they cost so much. Cost scared me away too.

Has anybody seen one up close?  It looks like if you had one on a shotgun, you wouldn't be able to have a front post on the end of the barrel.  Am I wrong?

Wow that went for cheap.... Last one in a regular auction I remember seeing went for $400.

You can't have a front sight.  

Hmm.  

I'd be willing to design one and possibly make a couple if people were interested.  Wouldn't be identical, but close enough.  

FYI... careful about those.  It looks like these were the early 'Nam version and not the most updated ones.  If you want that... go for it.  I personally like the newer version which has way more support and also a front post.



While I never seen one up close, only at a distance... it does not look like the one in your Ebay post.  It looks more like the one above.  Notice that the sandwich plate has a block on the inside... while the Ebay's one is hollow.  I 'embos' the photo to show that there is something there...

I would be interested in one, although I would prefer it be able to be used on more then just the 870.  I have been looking around for these also and $200 is the cheapest I could find.  I even spoke with a buddy that is an armoroer in the army and he said he hasn't seen them in a long long time.

Alright guys, I'm convinced.  
I'll at least try to design something, but I need some basic inputs as to features as to what it should be set up.    

First off, I need to know what make of ext tubes you have and some basic dimensions of that tube.  (Outer diameter of tube, length of ext, space between ext and barrel at narrowest point, etc.)

Secondly, what type of bayonet should it be set up for?  M6?  M7/M9? AK?

Third, should I try to make it so you can mount a light or sling on the side?

Any other things it should have?

Mods, this isn't intended as a sales thread, its just some research and brainstorming.  If I do sell them, I'll look into a dealer account.  Until then, this is just a design project.  

I will have to get you the numbers on my shotgun (its a maverick 88 so they should be the same as a Mossy 500), but I think a place to mount a sling on the side would be helpful.  I would prefer it to mount an AR bayonet as apose to the AK one.  Thanks and keep me informed plz.

I've seen several "one off" custom setups similar to the GI mount.

The easiest to make if you have the stamping equipment is a split unit.
This one was similar to a standard Remington barrel clamp only much longer, and was open on the top.
This allowed using the unit with a bead or rifle front sight.
In appearance, this looked pretty much like the above GI unit except it was open on top to clear sights and was tightened in place by the three screws between the magazine and barrel.

The bottom was fitted with a welded-on bayonet latch and a sling swivel.  One had an actual loop swivel, the other had a standard sling mounting stud so the swivel could be detached.
This particular unit was actually machined from bar stock, since the maker didn't have access to heavy-duty metal stamping and forming presses.
A stamped version would be far easier and faster to make, since it could be stamped and formed from heavy plate sheet steel.
The down side would be the cost of the metal stamping press and the cost of the dies.

The second unit was a welded-up unit.  
It was made from tubular steel with steel blocks welded between the two tubes.
The two steel tubes were slotted open and steel blocks were welded between the two tubes.
This made a figure-8 arrangement.
When screws through the blocks were tightened, the tubes snugged up around the barrel and magazine tube.
Again, a bayonet latch and sling loop were welded on the bottom

For fitting, this won't be a big problem since most extensions are very close in diameter.
The most sold extensions are.
Choate.
Remington factory.
Tac-Star.
Wilson.

For length, all that's necessary is that it fit the shortest setup which will be for an 18" barrel and 6 shot tube.  If it will fit that, it will fit longer setups.

For the bayonet latch, I'd suggest it be for the M7 and M9 AR-15 bayonets, since these are the most common and easiest to find at a lower price.

So, how you'd do this depends on your equipment.
The bar stock version would be very expensive due to the massive block of metal needed and the amount of man and machine hours to machine it out.

The welded tube design would be much faster and cheaper.

To allow attachment of accessories, all that's needed are accessory holes in the side blocks between the tubes.
Sling swivel mounts could be as simple as a hole through which a long sling stud could be passed and fastened with a nut.
flashlight mounts would be a simple accessory mount that also passes through holes and fastens with mounting screws and nuts.
Something like a standard Weaver mount bar with attaching screws and nuts would allow mounting many accessories.

My initial sketch is for a milled unit.  Goin to be a lot of machining, but I don't have the time, $$$, or know how to mess with sheet metal dies.  (I do have access to CNC machines.)

Anyway, the 2 reasons I need the dimensions are a.) I only have a Wilson +1 ext, and 1.) I'll pick the largest dimension and go from there.(It'll primarily rely on the barrel for strength and rigidity so it won't risk damaging the magtube.)

Here's some pictures of mine off my M870 clone build if you want to check it out.

beaniam.com/guns/mark1.JPG
beaniam.com/guns/mark1-2.JPG
beaniam.com/guns/mark1-3.JPG
beaniam.com/guns/mark1-4.JPG

To show that a +2 extension and 18" barrel can be used as well.
http://beaniam.com/guns/mark1-6.JPG
http://beaniam.com/guns/mark1-7.JPG

beaniam.com/guns/M870_done.JPG

Quoted: Here's some pictures of mine off my M870 clone build if you want to check it out. beaniam.com/guns/mark1.JPG beaniam.com/guns/mark1-2.JPG beaniam.com/guns/mark1-3.JPG beaniam.com/guns/mark1-4.JPG To show that a +2 extension and 18" barrel can be used as well. http://beaniam.com/guns/mark1-6.JPG http://beaniam.com/guns/mark1-7.JPG beaniam.com/guns/M870_done.JPG

Jconnet,

Does the middle screw on the adapter fit into the grove on the mag extension to lock the adapter in the proper position? It looks like it sits lower than the front/rear screw.

Yes, the middle screw goes through the groove in the extension to lock it in place.

Ok guys,

Here is my initial CAD drawing.  Not done yet, but the basic shape is there.  



If anyone has a Remington Factory +2 ext they'd be willing to trade for a Wilson Combat +1 ext. please IM me.  Also, if anyone has a beat up, rusty M7 Bayonet they'd be willing to donate or sell real cheap, please IM me.  (All I need is the Grip section and Hilt for measurement and fitting.)

New Screenies will be posted this evening.  

Still need those dimensions. . . .

I have the lug, m7 bayonet, and a micrometer.  What dimensions do you need

When I get home I will try and get you dimensions.  From those pictures it doesn't look like you  have anything locking the clamp to the mag extension.  Why not offset one of the screws so it goes in the factory extension's lock screw groove?

Well, I'm kind of leery about having it exert much force on the Mag tube, cause the 870 mag tube is rather thin and fragile and if damaged, will put the shotty out of action.  

Plus, not all extensions have that groove.  But I can redesign it if you guys want me to.  

Krazny13  Can you give a ballpark price at this time or will you need to make one first to know?  Just wonderin....

Measurements email sent.

Without a screw in that groove like on the +3 and +2 factory Remington mag extensions even with 4 clamping screws there's a chance you'll run into the whole assembly creeping off from firing.

Quoted: Krazny13  Can you give a ballpark price at this time or will you need to make one first to know?  Just wonderin....

I'll have to prototype 'em before I start to think about pricing.  Once I get a finalized design in the computer that meets my design criteria, and my standards of quality, I'll look into production, sales, etc.  

So please don't ask when and how much they'll be ready.  Mostly cause I dunno, and also cause the Admin on here are rather happy to enforce the 'non-paying dealer' rule, and they'd ban me real quick.        

Quoted: Measurements email sent. Without a screw in that groove like on the +3 and +2 factory Remington mag extensions even with 4 clamping screws there's a chance you'll run into the whole assembly creeping off from firing.

Good point.  
I'll add that feature in the next revision.


If you guys have any features in particular, feel free to suggest them.  If there's enough interest in mounts for non-Remington Shotguns, I'll design some.  

Im a cad draftsman, I have plans for a bayonet lug mount. If there are any guys that work in a machine shop maybe we could work something out.

_

Quoted: Has anybody seen one up close?  It looks like if you had one on a shotgun, you wouldn't be able to have a front post on the end of the barrel.  Am I wrong?

I was issued a M870 during the first Gulf War, and it had the bayonet adapter/front sight assembly.  Mine, along with every other one that I have seen was missing the front sight.

Slightly off topic, I realize its not a Remington 870, but if anyone has a Saiga-12 they want a bayonet on, Tromix has bayonet lugs for $55...

Hey guys
Bit of an update.

Been working on a slightly improved design.  Should have updated CAD pics later next week.  

If it was possible to make one that would work in conjunction with the Scattergun tech front sight I think that would be great.

If you don't mind IM ing me the width of the Scattergun Tech Front sight, I can change the design to make sure it will.  

Latest Revision:







Unless anyone has any objections or anything they want added, Thats pretty much the final configuration.  Other than some slight dimension adjustments, and maybe a couple barely noticable geometry tweaks.  Or some changes to allow production.  

If you guys want to make sure something will fit, IM me the measurement, and a discription, and I'll check and mod the design to make sure it will.  

Thanks,
Kraz

 I really like the look of that if and when I list developes I would like to get on it.


It Looks like you have made the stepped part for the bayonet ring a part of the bracket. Is there going to be a particular extension this will work with. Will it be dimensioned to fit the Scattergun tech, Vang and shoate tubes or will this work with just the remington factory extensions?

So far, the only one I have it set up for is the Wilson. (Because thats the only one I have to measure)
If you can get me a diameter on the other tubes I can clearance it so they will work.  

I don't post here much but I'm very intrigued by this thread. I have a choate tube on the way from midway. When it gets here I'll get you the dimensions. :) I'm going to have to have this item. :)

So, I'm looking at this a bit more. I have a couple questions. I know I'll feel stupid for asking this but, this slips over the mag extintion...correct? Also what is the width of the opening on the top? I also have a 20' remmy barrel with rifle sights on the way and I want to make sure it will be wide enough to fit passed my front sight. I'll get that deminsion when I get the barrel as well.

I orded the barrel and ext. on Jan 29th. The stuff was shipped on the 30th so it should be here any day.

clipse

According to my micro reader, the Remington Factory exension is exactly 1.000 inch in diameter. I would also be interested in a couple of these.

his.
There are options to stop creep, once we get something to mount!!!

Well, my stiff still didn't show up yesterday, so hopefully today. :)

Ok, I got my stuff Saturday. The Choate Extention is .910 wide.

I am going to have to tag this thread for an outcome.  Looks nice so far.

intrested in this project

Any new news?

clipse

I have been watching this for awhile and have to chime in.......

It looks as your are going to use those four holes to put screws through.  That is not going to work.  You going to CNC or mill this I assume?  The material you will be using will be far strong than almost all screws, not to mention the amount of torque required to compress the material would be far more than any screw driver or person could produce.  It will not compress the clamp to close on the barrel.  Even if you shave off some material on either side, I don't think it will work.  Using 6061-T6 instead of 7075-T6 won't make much of a difference either, both are incredibly strong.

You will also have to adjust for almost any barrel used and any extension which will require you RPT and test each one for fit then to CNC the actual part.  When trying to CNC a single piece substitute like this you are going to have to test after each alteration.

Remember, the Original Marine 870 system was a stamped sheetmetal piece.  You could easily screw it together so that it would fit practically any gun.  (Think about an AK stamped receiver and an AR receiver.  Put a screw through an AK receiver and a nut on the other side.  You can Tighten it, barely.  Try that with an AR receiver, unless your the Hulk it isn't going anywhere).  



I'm not trying to bust your balls.  But I originally designed mine like yours, but quickly changed my plan.  You have to think about the end-user requirements as well as the design.  Ideally you want to design a two peice system that clamps together, this will eliminate the need for redesign.  If you do a two peice system all extensions and barrels will be within your tolerences.  

Sry for the lack of updates.

Been doing some geometry tweaks off an on for the past couple days, as well as changing some dimensions.  

After shopping around to have it prototyped, It's become apparent that as designed the prototyping fee would be too much for this College student to afford.  

I'll be changing it to make it easier to machine.  

Quoted: I have been watching this for awhile and have to chime in....... It looks as your are going to use those four holes to put screws through.  That is not going to work.  You going to CNC or mill this I assume?  The material you will be using will be far strong than almost all screws, not to mention the amount of torque required to compress the material would be far more than any screw driver or person could produce.  It will not compress the clamp to close on the barrel.  Even if you shave off some material on either side, I don't think it will work.  Using 6061-T6 instead of 7075-T6 won't make much of a difference either, both are incredibly strong.

The material I was going to use was actually a bit softer than the screws.  (Yea, I know, not supposed to do that cause it'll make boogering the threads up easier.)  Also, as the clamp was pretty much designed to force fit over the barrel, you wouldn't need to tighten it too much to achieve the desired clamping force.  (Yea, I know.  Might scratch the barrels.)

You will also have to adjust for almost any barrel used and any extension which will require you RPT and test each one for fit then to CNC the actual part.  When trying to CNC a single piece substitute like this you are going to have to test after each alteration.

I never intended this to contact the mag ext. at all except for the end.  I am leery of bending the mag tube, and as a result designed it to avoid any type of force but an impact along the tubes center axis.(which should be absorbed by the barrel ring if the ext was tightened down to it.)  As for the different extensions, since I dont want it to contact the tube except for the end, I simply selected the largest OD of a mag extension made and used that (Plus a small clearance for manufacturing tolerance) to ensure it slid over the mag ext.        

Remember, the Original Marine 870 system was a stamped sheetmetal piece.

Yes.  Members here were kind enough to send me pics of originals.  However, the fact is that I lack access to sheet metal forming machinery, and I lack the funds to pay for a prototype from those that do.  Hence the CNC style design.  

I'm not trying to bust your balls.  But I originally designed mine like yours, but quickly changed my plan.  You have to think about the end-user requirements as well as the design.  Ideally you want to design a two peice system that clamps together, this will eliminate the need for redesign.  If you do a two peice system all extensions and barrels will be within your tolerences.

I'll be redesigning it anyway to lower the machining costs.  
And I don't mind the criticism.  I'm rather used to it as an Engineering Tech student.  

From looking at your latest drawing, you are not using one screw offset to line up with the factory Remington groove in the mag extension. I understand your concern about not stressing the mag tube, but please consider, the only reason there is a groove in the Remmy extension, is because Remington engineers found that the bayonet adapter will just move forwards or backwards from the recoil and/or the impact of ramming a bayonet into a person, without the groove providing a hard bearing surface. I am also not trying to be a wet rag, but I think it will not lock down tightly enough with just screw tension. You really need to use the Remington groove, as intended. Many people do not realize that the groove on police model extensions is a holdover from the Vietnam era military work by Remington. As far as the non-groove aftermarket extensions, I do not have a solution for you.  Best of luck!  

Any new news on this?