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Posted: 5/2/2008 4:29:16 PM EST
Well the goal is to build a semi-auto version of this.


I had no idea where to begin until about three weeks ago when I and a few others scored a set of handguards off the EE. It was my lucky day I thought. I'm going to build a M231. Since then, the enthusiasm shown for these handguards in the Garrison 633/DOE Sights Thread looks like it may be leading to some pretty nice reproductions being made!

So over the past three weeks with the help of a Retro Forum regular and some dumb luck on my own here is what I've put together.

-M231 Upper Receiver - New
-Adapter Bracket for Wire Stock - New
-Wire Stock - Looks Unused
-Selector Cover - New
-M231 Pistol Receiver Extension - Surplus, looks unused. Large OD, steel and heavy
-Handguards - Used, good condition

Since I have no experience with AR pistols, I have a lot more to learn about what carrier and buffer combo will work in this short of a tube. Don't know the exact overall length (approx 4 13/16"without cap) because I don't have the end cap that screws on the rear (see photo below). Even if I had the original drive springs and striker that go inside, they are not the ticket for a semi build.


The part that I'm told is impossible to find is the large threaded gas block that allows the weapon to be attached to its firing port like this:

Here's a close up:

If a repro is the only way to go, does anybody have one to take measurments from?
Are there any drawings/blueprints of these available?
A limited run of these by someone would be a big hit!

The more interest shown for these parts the more likely someone is to remake them.
Anyone else working on or thinking about a M231 build?
Suggestions, comments, advice?
I'll keep you updated on my progress.



Link Posted: 5/2/2008 4:34:10 PM EST
tag
Link Posted: 5/2/2008 4:37:24 PM EST

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?
Link Posted: 5/2/2008 4:43:28 PM EST

Originally Posted By Stryfe:

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?


I think that is the support bracket for sliding wire stock.
Link Posted: 5/2/2008 4:57:48 PM EST
tag


Link Posted: 5/2/2008 5:07:28 PM EST
[Last Edit: 5/7/2008 7:42:40 PM EST by peepshowal]

Originally Posted By Stryfe:

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?

Here on the EE


Link Posted: 5/2/2008 5:09:32 PM EST

Originally Posted By Stonerriflefan44:

Originally Posted By Stryfe:

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?


I think that is the support bracket for sliding wire stock.


No, the support is further back. Member Quiet has the selector cover FS in the EE last I checked.

What that front base (can't really call it an FSB now can I? ) reminds me of in shape is a PVC adapter from one size to another, with a square thread wrapped around it. Of course, PVC would be the WRONG thing to try and make it out of, #1 it would melt after a few mags, #2 the fumes are toxic, however, in mocking one up as a model for a machine shop to follow, it might be a good start. The threads look like the hard part to me, but I've known some really good fabricators who could do it. There are guys out there who would spend a lot of time on it just because it was a puzzle, and something new from welding on a bumper say, and who would charge you reasonably, but there's a lot of hours there. If you could give them a mock-up that fits to start with, and some good pics, it's doable. I know damn well there's a pile of these in plastic bags laying on a shelf somewhere...

The lack of sights is the only thing that turns me off on the project, as I LIKE sights. It would be very cool if you could get the ATF to sign off on an open bolt conversion, but it'd have to be a post dealer sample, built by a registered mfg, so I doubt it would ever happen - but there was one company offering a Class III open bolt conversion for LE not that long ago. The bolts even show up from time to time. Good luck with the build - I can't wait to see the finished product. IMO you've gone further than anyone else I've seen.
Link Posted: 5/2/2008 5:16:29 PM EST

Originally Posted By Stonerriflefan44:

Originally Posted By Stryfe:

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?


I think that is the support bracket for sliding wire stock.


They are two different parts. Here's a close up with the selector cover on left and the wire stock adapter bracket on right.
Link Posted: 5/2/2008 5:23:05 PM EST
Tagged for a cool thread.
Link Posted: 5/2/2008 5:26:28 PM EST

Originally Posted By Morg308:

Originally Posted By Stonerriflefan44:

Originally Posted By Stryfe:

Originally Posted By scottryan:
tag

totally

Where did you find the selector cover?


I think that is the support bracket for sliding wire stock.



. I know damn well there's a pile of these in plastic bags laying on a shelf somewhere...

I really hope you're right about that!


Originally Posted By Morg308:
The lack of sights is the only thing that turns me off on the project, as I LIKE sights.

There is still the hole in the carry handle for some type of optic. OEG maybe?
Link Posted: 5/2/2008 5:38:08 PM EST
[Last Edit: 5/2/2008 5:40:03 PM EST by postino]
If I were going to make one of those FSB/port adapters...

I'd make it out of aluminum, and turn it to the size needed except for the "screw"...

You could probably figure out the pitch, and maybe even thread it on a lathe...and pack at least one lunch while doing it...

Or you could mount a used 4 1/2" Mikita grinder disk (with a rounded edge) in a tool post grinding attachment and grind it slowly...maybe using a big bolt (and nut in the lathe chuck) as a mandrel...screwing the bolt (with FPW FSB attached) in and grinding the big thread gradually...

I know there is a shop near me that does things like this because I had to get quotes on turning a worm steering gear for a British sports car in years past...They mill the groove on a special mill/lathe that advances and rotates the work as the mill cutter cuts...

Interesting project...for someone...
Link Posted: 5/2/2008 5:42:51 PM EST
I know zero about these rifles, but I saw the term open bolt and I saw this on GunBroker. If it doesn't apply to your build I apoligize for wasting your time.
http://www.forthehunt.com/Auction/ViewItem.asp?Item=98611116
Link Posted: 5/2/2008 6:13:38 PM EST
[Last Edit: 5/2/2008 6:17:29 PM EST by peepshowal]

Originally Posted By GUTS:
I know zero about these rifles, but I saw the term open bolt and I saw this on GunBroker. If it doesn't apply to your build I apoligize for wasting your time.
http://www.forthehunt.com/Auction/ViewItem.asp?Item=98611116


Yes, that looks like the striker. From what I've read it replaces the hammer on the small end by sliding inside of the bolt carrier and striking the head of the firing pin.
On the hollow large end it retains three springs fitted inside of each other that run the length of the receiver extension. The rubber recoil buffer/washer fits against the cap end of the receiver extension.

edited to make the
Link Live




Link Posted: 5/2/2008 6:33:09 PM EST
20 years ago it would have been a piece of cake to build a M231. Now you rarely or never see the parts. Building a M231 with original parts would be extremely hard now.
Link Posted: 5/2/2008 6:42:20 PM EST
[Last Edit: 5/2/2008 6:43:59 PM EST by QUIET]
peepshowal,

Its really coming along great, congrats! That's an interesting gunbroker auction but I hadn't seen the 3 rubber washers before. Hmmm.

Threaded gas blocks. Hmmm....

Nice score on the receiver extension. Did that turn up out west?

Link Posted: 5/2/2008 6:53:55 PM EST

Originally Posted By QUIET:
peepshowal,

Its really coming along great, congrats! That's an interesting gunbroker auction but I hadn't seen the 3 rubber washers before. Hmmm.

Threaded gas blocks. Hmmm....

Nice score on the receiver extension. Did that turn up out west?



Thanks and yes it did.
Link Posted: 5/2/2008 7:08:08 PM EST
I've been working up a solution to this for some time.

You are going to have to mill the left wall of your lower down to fit the sideplate correctly.

A regular hammer/trigger will have to be used along with a regular bolt/carrier.

You still should be able to use the nested springs and buffer of the original M231.

Link Posted: 5/2/2008 8:00:27 PM EST
I think you can do it, but you will have to skip the collapsible stock, otherwise it becomes an SBR; without the wire stock, then you can registered as a pistol and you are G2G.
Link Posted: 5/2/2008 8:36:59 PM EST
[Last Edit: 5/2/2008 8:38:19 PM EST by blackta6]

Originally Posted By scottryan:
You still should be able to use the nested springs and buffer of the original M231.


Now wait, the buffer is the striker in the M231. How are you going to use it in conjuntion with a standard semi-auto carrier?
Link Posted: 5/2/2008 9:09:20 PM EST
Peepshowal, you've got a great collection of parts there. I know I'll be watching for the front gas block every time I go to a gun show from now on. I have no plans on trying to do a build like this but, I'd love to see someone here do it and if I run across the gas block it's yours.

Doc
Link Posted: 5/2/2008 11:26:43 PM EST
[Last Edit: 5/2/2008 11:32:29 PM EST by hk45shooter]
Excuse me but with that wire stock on there it would be considered a SBR, not a pistol, right? What does the state of CA have to say about that?

ETA: Sometimes it just pays to read the whole thread before posting, Black-Tiger beat me to it.
Link Posted: 5/2/2008 11:32:18 PM EST
[Last Edit: 5/2/2008 11:34:19 PM EST by Hunterex]

Originally Posted By hk45shooter:
Excuse me but with that wire stock on there it would be considered a SBR, not a pistol, right? What does the state of CA say about that?


I've seen other weapons with folding, telescoping stocks frozen in the closed position pass the F troop's qualifications of a pistol. Maybe that's a possibility here.

EDIT : But maybe he'll be using a 16" barrel...
Link Posted: 5/3/2008 3:53:25 AM EST
[Last Edit: 5/3/2008 3:54:19 AM EST by CB1]
That is a good start to the project.

It would be a great novelty item to have in the collection for sure!

if you can work up the threaded fore end, it would be cool as shit to find the ball mount and to screw the M231 into for display.

Great job so far! and I'm glad my picture inspired a project!

ETA - as soon as I replace my scanner, I'm going to scan the negative at a high resolution to get more details out of that picture for every to use.
Link Posted: 5/3/2008 3:56:50 AM EST
Just found it on GUnbroker

www.gunbroker.com/Auction/ViewItem.asp?Item=98753057

An M231 upper.
Link Posted: 5/3/2008 4:15:21 AM EST

Originally Posted By blackta6:

Originally Posted By scottryan:
You still should be able to use the nested springs and buffer of the original M231.


Now wait, the buffer is the striker in the M231. How are you going to use it in conjuntion with a standard semi-auto carrier?




The buffer/striker would have to be cut back or a new one fabricated.
Link Posted: 5/3/2008 4:51:04 AM EST
Link Posted: 5/3/2008 7:56:27 AM EST
A while back the same guy on gunbroker that has 231 parts also had NIW 231 bolt.

You might email him and see if he still does, if ya haven't already.

Looks good, good luck with the build.

Hal
Link Posted: 5/3/2008 8:01:10 AM EST
[Last Edit: 5/3/2008 8:14:30 AM EST by peepshowal]

Originally Posted By Black-Tiger:
I think you can do it, but you will have to skip the collapsible stock, otherwise it becomes an SBR; without the wire stock, then you can registered as a pistol and you are G2G.


Both you and hk45shooter bring up issues that I'll have to deal with to satisfy both Federal and California law.
I've read that the barrel on the original is 15.6" long. If that is correct, then a pinned flash hider or a 16" should be easy and still look correct.

Overall length of 26" for federal should be met even with stock callpsed. California ups the OAL to 30" to keep out of assault weapon territory. May have to fix the stock in the extended position or make it so it will not collapse to less than 30."

The final California legal hoop to jump through requires using a "Bullet Button" mag release that allows the mag to be removed only with the push of a tool (bullet tip). Then legally one's rifle does not have a detachable mag and all the evil features can be added.
Please do what you can to keep these laws from comming to a state near you.

Doc Mike- That is very kind. Thank you! I need all the help I can get.

CB1- Glad you're not upset I used a photo that is yours. Thank you. Would love to see more high resolution photos!
Link Posted: 5/3/2008 8:41:08 AM EST

Originally Posted By peepshowal:

Originally Posted By Black-Tiger:
I think you can do it, but you will have to skip the collapsible stock, otherwise it becomes an SBR; without the wire stock, then you can registered as a pistol and you are G2G.


Both you and hk45shooter bring up issues that I'll have to deal with to satisfy both Federal and California law.
I've read that the barrel on the original is 15.6" long. If that is correct, then a pinned flash hider or a 16" should be easy and still look correct.

Overall length of 26" for federal should be met even with stock callpsed. California ups the OAL to 30" to keep out of assault weapon territory. May have to fix the stock in the extended position or make it so it will not collapse to less than 30."

The final California legal hoop to jump through requires using a "Bullet Button" mag release that allows the mag to be removed only with the push of a tool (bullet tip). Then legally one's rifle does not have a detachable mag and all the evil features can be added.
Please do what you can to keep these laws from comming to a state near you.

Doc Mike- That is very kind. Thank you! I need all the help I can get.

CB1- Glad you're not upset I used a photo that is yours. Thank you. Would love to see more high resolution photos!




IMHO, you shouldn't be doing this project if you have to pin the stock in place.
Link Posted: 5/3/2008 10:23:24 AM EST
As long as we're on the subject of M231s, here's a couple photos to ponder. I've had this gas block for a while and always thought it was for the port fire weapon. But it sure isn't the style with the large external thread. So is this an earlier or later model? Or is the threaded part a piece that goes over this part? Anybody know for sure?

http://photos.imageevent.com/ricklarson/gunparts/large/PICT0767.JPG

http://photos.imageevent.com/ricklarson/gunparts/large/PICT0769.JPG

http://photos.imageevent.com/ricklarson/gunparts/large/PICT0771.JPG
Link Posted: 5/3/2008 10:57:59 AM EST

Originally Posted By ordnance:
As long as we're on the subject of M231s, here's a couple photos to ponder. I've had this gas block for a while and always thought it was for the port fire weapon. But it sure isn't the style with the large external thread. So is this an earlier or later model? Or is the threaded part a piece that goes over this part? Anybody know for sure?

photos.imageevent.com/ricklarson/gunparts/large/PICT0767.JPG

photos.imageevent.com/ricklarson/gunparts/large/PICT0769.JPG

photos.imageevent.com/ricklarson/gunparts/large/PICT0771.JPG


There were three different prototype designs (according to the book "Black Rifle") of firing port mounting points. Your pictures look like one of them. There is a picture of that mount on page 361 in the book "Black Rifle".
Link Posted: 5/3/2008 11:18:41 AM EST

Originally Posted By hk45shooter:
There were three different prototype designs (according to the book "Black Rifle") of firing port mounting points. Your pictures look like one of them. There is a picture of that mount on page 361 in the book "Black Rifle".


Yep - Sure looks like the middle pic. I can't take a good scan/pic to save my life, but maybe someone else can...
Link Posted: 5/3/2008 11:29:50 AM EST

Originally Posted By postino:

Originally Posted By hk45shooter:
There were three different prototype designs (according to the book "Black Rifle") of firing port mounting points. Your pictures look like one of them. There is a picture of that mount on page 361 in the book "Black Rifle".


I can't take a good scan/pic to save my life, but maybe someone else can...


Me either, that's why I just referenced the book & it's page.
Link Posted: 5/3/2008 11:40:53 AM EST
[Last Edit: 5/3/2008 11:42:14 AM EST by postino]
Lemme give it a shot...



The mutilated stub is a great find...but it's a shame it was dewatted in the first place...

(This is the "center" pic noted in the description)
Link Posted: 5/3/2008 12:59:44 PM EST

Originally Posted By scottryan:

Originally Posted By peepshowal:

Originally Posted By Black-Tiger:
I think you can do it, but you will have to skip the collapsible stock, otherwise it becomes an SBR; without the wire stock, then you can registered as a pistol and you are G2G.


Both you and hk45shooter bring up issues that I'll have to deal with to satisfy both Federal and California law.
I've read that the barrel on the original is 15.6" long. If that is correct, then a pinned flash hider or a 16" should be easy and still look correct.

Overall length of 26" for federal should be met even with stock callpsed. California ups the OAL to 30" to keep out of assault weapon territory. May have to fix the stock in the extended position or make it so it will not collapse to less than 30."

The final California legal hoop to jump through requires using a "Bullet Button" mag release that allows the mag to be removed only with the push of a tool (bullet tip). Then legally one's rifle does not have a detachable mag and all the evil features can be added.
Please do what you can to keep these laws from comming to a state near you.

Doc Mike- That is very kind. Thank you! I need all the help I can get.

CB1- Glad you're not upset I used a photo that is yours. Thank you. Would love to see more high resolution photos!




IMHO, you shouldn't be doing this project if you have to pin the stock in place.


Thank you scottryan. I am not sure that the stock will have to be fixed to meet the minimum length. It will be close so perhaps a slightly longer barrel or muzzle device may be needed though that may not look correct. If the stock does need to be fixed (not pinned) I believe it can be done without altering or damaging any original part if that is your concern. Just a device or collar around the 2-position stock adjuster button that keeps it from being pushed. This could also be undone if one's state residency were to change.
Link Posted: 5/3/2008 3:56:25 PM EST
Oh awesome
Link Posted: 5/3/2008 4:38:53 PM EST
Just use a HBAR 16" barrel....close enough and should be long enough.
Link Posted: 5/3/2008 5:07:03 PM EST
i was thinking a guy could use a modern gas block and make a slip over screw/front cap. just hold it in place with a set screw or 2 on the bottom out of sight.
Link Posted: 5/3/2008 5:25:20 PM EST
I have an idea for the gasblock. How about turning the shape of the gas block on a lathe, then finding a suitable spring to cut a couple of links out of for the appearance of the thread? You could just tack weld each end of the coil and blend it with a Dremel.
Just a thought.
Link Posted: 5/3/2008 6:03:53 PM EST

Originally Posted By my65pan:
I have an idea for the gasblock. How about turning the shape of the gas block on a lathe, then finding a suitable spring to cut a couple of links out of for the appearance of the thread?


Motorcycle rear shock/spring maybe??? About the right size, I think...You'd have to make the gas block out of steel to weld a spring to it though...
Link Posted: 5/3/2008 6:25:56 PM EST
How about taking some 1/8" or so square stock, heat it up red hot, wrap it around a mandrel to cool, then tack a couple of turns of that on.
I'm just thinking out loud here.
Link Posted: 5/4/2008 5:07:46 AM EST
Does anyone have a picture of all the M231 parts laid out? I remember reading it was a unique open bolt set up.
Link Posted: 5/4/2008 5:28:26 AM EST

Originally Posted By Bucknakedracin:
i was thinking a guy could use a modern gas block and make a slip over screw/front cap. just hold it in place with a set screw or 2 on the bottom out of sight.


This is along the lines of what I had in mind. If you could fabricate a close approximation of the original gas block from wood or plastic, then sand cast a copy. Simply slip it over a low profile gas block and pin or set screw in place.
Link Posted: 5/4/2008 8:04:51 AM EST

Originally Posted By slt223:
Does anyone have a picture of all the M231 parts laid out? I remember reading it was a unique open bolt set up.


Yes, the 231 is open bolt, full auto only. I have an electronic version of the RPSTL (parts catalog). I can pull the pages that show all the installations or just post the PDF file.

I am a test engineer for BAE Systems, the designers/builders of the Bradley Fighting Vehicle. Since the FPW has all but been eliminated from the Bradley, we only have 1 FPW left in our arsenal for fit-ups. We have an extremely difficult time getting replacement parts for this 1 remaining gun. Even Colt's doesn't have or make parts for it any more. All the piece-part drawings are still available from Colt's.
Link Posted: 5/4/2008 8:41:42 AM EST
[Last Edit: 5/4/2008 8:41:50 AM EST by Dawg180]
Russ,

If you could take photos/measurements of the M231 gas block you would be a hero around here!
Link Posted: 5/4/2008 8:43:54 AM EST
[Last Edit: 5/4/2008 8:44:04 AM EST by Dawg180]

Originally Posted By postino:
Lemme give it a shot...

i23.photobucket.com/albums/b390/FrogBait4/Mil/fpw.jpg

The mutilated stub is a great find...but it's a shame it was dewatted in the first place...

(This is the "center" pic noted in the description)


If I was to hazard a guess, looks like that version may have been retained with a spring loaded corss pin through the slot on top, or maybe it was inserted at 90 degrees and then rotated vertical, knind of like a keyway.
Link Posted: 5/4/2008 8:44:26 AM EST

Originally Posted By Russ4777:

Originally Posted By slt223:
Does anyone have a picture of all the M231 parts laid out? I remember reading it was a unique open bolt set up.


Yes, the 231 is open bolt, full auto only. I have an electronic version of the RPSTL (parts catalog). I can pull the pages that show all the installations or just post the PDF file.

I am a test engineer for BAE Systems, the designers/builders of the Bradley Fighting Vehicle. Since the FPW has all but been eliminated from the Bradley, we only have 1 FPW left in our arsenal for fit-ups. We have an extremely difficult time getting replacement parts for this 1 remaining gun. Even Colt's doesn't have or make parts for it any more. All the piece-part drawings are still available from Colt's.


Wow! That's great! Please post the PDF file. Thanks
Link Posted: 5/4/2008 10:17:07 AM EST
[Last Edit: 5/4/2008 10:24:51 AM EST by Bucknakedracin]
i would think you would have to make the hand guard cap on a cnc mill not a lathe. on the lathe you could certainly turn a thread but it would be just that.. a thread. you would still have all of the material between the threads.
on a cnc mill you could set it up to machine the thread(which doesnt have to function) and remove the material between the threads. make sense? well to me it does lol.
Link Posted: 5/4/2008 10:23:39 AM EST

Originally Posted By Bucknakedracin:
make sense?


......

<­BR>......
Link Posted: 5/4/2008 12:04:21 PM EST

Originally Posted By Russ4777:

Originally Posted By slt223:
Does anyone have a picture of all the M231 parts laid out? I remember reading it was a unique open bolt set up.


Since the FPW has all but been eliminated from the Bradley, we only have 1 FPW left in our arsenal for fit-ups.


No problem. Just ship that FPW to one of our more talented machinists for a couple weeks and we'll get you all the spare parts you need!

Seriously though, specs on the part being discussed would really make you a hero. Just out of curiosity - what replaced the FPW? IIRC it was just flip-open ports? I bet the ball mechanism gets pretty damn gritty and hard to move in the desert sand...
Link Posted: 5/4/2008 12:17:15 PM EST

Originally Posted By Bucknakedracin:
i would think you would have to make the hand guard cap on a cnc mill not a lathe. on the lathe you could certainly turn a thread but it would be just that.. a thread. you would still have all of the material between the threads.
on a cnc mill you could set it up to machine the thread(which doesnt have to function) and remove the material between the threads. make sense? well to me it does lol.


Makes sense to me - the wide, square cut of the 'valleys' were obviously done with CNC. OTOH,I was a robotics major in the early '80s and remember when CNC was 'the next great thing' Now it's common. So common that the knowledge of how to set-up an Non-CNC machine is becoming extinct...

Alternately, I like the idea about square stock being heated and wrapped around it. pretty easy to do with a forge. (My dad's a blacksmith) But if it were spot welded in place, you'd need a sharp carbide bit and a dremel to remove the weld material so it looked right. No biggy, just more work.

Once we get the OD specs, someone should check Graingers or McMaster-Carr for weld-on pipe adapters. I'm guessing a 1-1/4 or 1-1/2 to 2" adaptor might work. When I get into work next week I'll check Grainger, see what they have.
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