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[ARCHIVED THREAD] - 656 questions (Page 1 of 3)
Posted: 11/1/2010 5:03:22 PM EDT
I have a request to help a member build a 656 clone. Does anyone have any specs on this upper? What I really need to know is what sort of rail was used for the scope mount. There appears to be a rail cut into the front, upper portion of the receiver to accept scope rings etc.
I made up a couple of blanks today for the de-milled receiver that was sent to mock up this project. I didn't have the photo with me and the only specs I had were for a 1913 rail so I did a practice run, remember this was pulled from my feeble short term memory on the fly. I realize I didn't get very close, but at least I know I can duplicate the sight wheel/spring pocket dimensions etc. and I can machine a rail. 
Any info would be greatly appreciated. |
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The rear sight pocket dimensions may not be standard, as the 656 apparently had some type of flip-up rear sight. As far as I know, no one has obtained or posted a photo of the rear sight assembly. The pocket could be more or less standard, but the aperture would have to have a long "arm" where the L-marked aperture normally is.
Here's a better picture of the "rail" for you: 
ETA: Quoted:
are you makin' more than one? If yes, I'm in for one. |
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really wish I had the information to help out on this, as I wanted to see one of these done for quite some time now
is this going to be built off of a modified flat top? are you makin' more than one? YHM makes a riser that could probably be modified into your mount 
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The rear sight pocket dimensions may not be standard, as the 656 apparently had some type of flip-up rear sight. As far as I know, no one has obtained or posted a photo of the rear sight assembly. The pocket could be more or less standard, but the aperture would have to have a long "arm" where the L-marked aperture normally is. Here's a better picture of the "rail" for you: http://img527.imageshack.us/img527/7724/vintagesniperupper.png ETA: Quoted:
are you makin' more than one? If yes, I'm in for one. Thanks, that stripped upper photo helps a lot. The scope rail needs to be about 5/8" wide to fit within the width of the upper. I'm just wondering what scope mounts fit within 5/8" wide. This is just a mockup, the portion I machined is bolted to the de-milled A1 upper that I cut the handle off of and milled flat. Once I get the dimensions/appearance right it is to be welded to a similarly modified good upper, re-machined/blended, and then anodized. One is all I'm in for at this point, just helping out another retro member that's all. |
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Shouldn't be too hard.
1.) Partial Fence lower 2.) Dimpled selector 3.) A1 barrel 4.) Flat Slip ring 5.) Front sight you could machine the top and add a 91/30 front sight globe 6.) Can't tell, but an A1 or possibly A2 flash hider 7.) Looks to be a Type D stock 8.) A1 handguards 9.) Machine an upper like what your first post looks like. 10.) Scope mount and scope The upper will be the hardest part. |
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Shouldn't be too hard. 1.) Partial Fence lower 2.) Dimpled selector 3.) A1 barrel heavy barrel 4.) Flat Slip ring 5.) Front sight you could machine the top and add a 91/30 front sight globe 6.) Can't tell, but an A1 or possibly A2 flash hider 7.) Looks to be a Type D stock 8.) Machine an upper like what your first post looks like. |
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Rail looks like an old style Weaver rail, which would dovetail with the era of the 656. Pun intended? Seriously though, that's the thing I'm wondering about. It would make sense for it to be a Weaver rail, but the pictures leave me uncertain. Weaver and Picatinny rails have the same cross-section. Anyone who owns a flat-top upper or looks at my65pan's pictures above can see that the rail is wider than the sides of the receiver directly below it. Now, granted, it's kind of hard to tell in the picture of the stripped upper, but it doesn't look like the rail is any wider than the receiver. If it were, it wouldn't need the radiused recess immediately below, which appears to be the same depth as the larger recess that runs along the side (which I assume is just a weight-saving measure). So I'm not sure that it actually is a Weaver rail at all. |
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Rail looks like an old style Weaver rail, which would dovetail with the era of the 656. Pun intended? Seriously though, that's the thing I'm wondering about. It would make sense for it to be a Weaver rail, but the pictures leave me uncertain. Weaver and Picatinny rails have the same cross-section. Anyone who owns a flat-top upper or looks at my65pan's pictures above can see that the rail is wider than the sides of the receiver directly below it. Now, granted, it's kind of hard to tell in the picture of the stripped upper, but it doesn't look like the rail is any wider than the receiver. If it were, it wouldn't need the radiused recess immediately below, which appears to be the same depth as the larger recess that runs along the side (which I assume is just a weight-saving measure). So I'm not sure that it actually is a Weaver rail at all. I've been wondering the same thing, but if you look at the stripped upper it appears that the rail is slightly wider than the upper. I think I can see a shadow at the rear edge of the rail. The demilled upper I chopped up has a width of about .660 and the Weaver/Picatinny dimensions call for .617 maximum width under the rail, so a slight recess is required. You can see the recess I milled under the rail on the trial run photos above. The radiused appearance of the recess may be how it was forged with the rail cut into it after the fact. A lot of ifs on this one. ETA: Forgive my MS paint skills, but this is sort of what I meant, with the black lines showing the rough forging and the red showing the machined rail. Just a guess though. 
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As a practical matter, if I were making a clone, I would go with a Weaver rail, because you're going to need a mount to fit it, unless you are so unbelievably lucky as to own one of the pictured original AR TEL mounts for the 656. And if we already had the mount, we wouldn't have to be debating the specs of the rail.
For what it's worth, Wikipedia says Weaver rail, but does not cite a source. |
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Isn't there a PRE-Weaver Dovetail rail on some older firearms, which was narrower, and flatter than modern weaver/picatinny? I'd be interested in dimensions of that. I'm pretty confident I can machine a reasonably close clone if I have the right info. Does someone have the skills to blow up the photo of the stripped upper and extrapolate dimensions from known measurements of a regular upper? I'd like to get a better idea of exactly where the sight wheel is located, where the recesses are, their length ,width etc. in relation to say the charging handle slot or ejection port opening. I'd like to make this as close as I can and save all of the info for possible future 656 builds. |
I can and have enlarged the photo, but there is only so much data one can glean from it. Increasing the size sadly doesn't increase the resolution... it doesn't work the way it does on "CSI" on TV. 
I really can't tell any more about the rail, but let me work on the rear sight wheel location. I'll update this post in a while after I play around with it in Photoshop for a bit. Okay here we go... First thing I've learned, the bottom of the lower recess appears to be exactly in line with the top of the charging handle slot. The little bit of darkness below the blue line in the charging handle slot is just because the photo wasn't taken from exactly square to the receiver and we are seeing a little bit of the underside. Yes, I realize this is annoying from an actually-building-the-damn-thing perspective. Height is around 2.645" from the pivot pin datum (center) to the top of the rail. Compared to 2.125" for a standard flattop, this makes the rail about 0.52" higher than a modern flattop. This measurement is approximate and may be slightly on the low end. Height of the rear sight protective "ears", as measured from the top of the charging handle slot (blue line) to the top of the ears, is approximately 0.93"-1.0". Width of the lower recessed groove is approximately 0.35"-0.36". The groove is about 5.13" long overall, or 4.78" excluding the radii at the ends. The mounting rail is about 4.45" long from the front face of the receiver (the face, not the barrel threads) to the rearmost point of the radiused groove, or about 4.275" long excluding the radius. The rear sight wheel is located approximately 5.9" back from the front face of the receiver. Or, it is approximately 0.67"-0.70" forward from the center of the rear takedown pin. Vertically, the center of the rear sight wheel is approximately 0.54"-0.58" up from top of the charging handle slot. The center of the front slot in the rail is approximately 0.50" behind the front face of the receiver. The rear slot is about 3.677" back from same. If anyone wants to play with the below image themselves, the scale is approximately 31 pixels per inch. 
Okay I'm done for now. If anyone has any specific questions feel free to post or IM and I'll respond when I can. |
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The one thing that worries me is that the lower recess slot looks to be situated at about the same place the sight/rail assembly will be welded to the donor upper. I may have to cut it a little deep into the rail and then re-machine the recess after it's welded. It can't go much lower without getting into the charging handle slot.
ETA: Thanks for the effort flatdarkmars, I understand that the photo will pixelate etc. but I'm about as skillful with photoshop as I am with MS paint.
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Bump for my post above updated with measurements extrapolated from the image. Questions? IM or post here.
ETA: It occurs to me that the location of the rear sight (in a fore-aft direction) really ought to be the same as that of a regular A1 rear sight, in order to keep the sight radius and thus the sight adjustments the same. But I think the A1 rear sight is more than 0.70" forward of the rear pivot pin... I can't measure it exactly with what I have at my disposal, nor can I find drawings online for anything other than a flat top upper. Then again, considering that the 656 front sight also appears to be non-standard, who knows? Also, the pop-up sight arm could have been inclined for all we know... |
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Bump for my post above updated with measurements extrapolated from the image. What I did was blow up the pic (that was posted last year) up to life size and pull my dimensions right off that... If anyone knows how to Search the Archives, there are a couple good clear pics in a thread somewhere... 
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Cool project OP. How about putting in a 5 or 10 degree down angle on the underside of the "upper-upper" you're making? It would be helpful for longer ranges and scopes that would run out of elevation adjustment...
Edit: or rather, would it be an up angle (back to front) that when layed level on the under-upper, would properly set the MOA rake? |
One more picture, just because:
NDS-603 for comparison. The rear sight wheel is definitely aft of where it is on a standard A1. ETA: The lower groove is a bit longer than the opening in the carry handle. One of the archived threads I read said that the originals were not made from a unique forging, but from a piece of bar stock attached to the top of a shaved receiver. I strongly suspect that the lower groove was machined after the new top piece was attached, in order to hide the small groove that is apparent in your mock-up photos where the carry handle opening would have been. |
Looking good there bud!
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I'm constantly impressed with the talents here!  My wallet sure isn't. 
Seriously, this was one variant I was really interested in (heavy barrel, flat top and RETRO) but the exorbitant cost made it comfortably out of my puny reach. If you guys start this, I may have to dive in as well. Dammit! |
Looking good! 
Constructive critique here... on the real 656 upper, the front of the lower groove is more or less in line with the front of the ejection port, while on your current mock up it looks a little bit too far forward. I believe you have the overall length of the groove about right (I assume you used the measurements) but because it is slightly too far forward, the rear of the groove is a bit further from the sight wheel holes than on the original. The top groove looks off somehow as well, but I think you are correct about it just needing a little widening and it may be good then. Part of me is glad that you're calling this a one-off project so far... because I really don't need to start another build right now. Hell, if I did a 656 then I'd have to expand my US service rifles collection to include sniper variants... oh dear. 
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| This isn't the mock up anymore, the lower recess will be widened a little towards the top and maybe lengthened a smidge towards the rear once I get a sight wheel in my hands, but it is what it is. The recess under the rail may stay as is depending on how it looks when the scope mount arrives. I was using the picture of the assembled rifle to judge where the lower recess ends at the front, it looks like it ends forward of the port door in that photo so that's what I went with. The funny thing is it's also exactly where the radius of the carry handle I cut off ended, makes me wonder if these were forged as is, or A1 forgings were modified before machining on the original 656s? |
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This isn't the mock up anymore, the lower recess will be widened a little towards the top and maybe lengthened a smidge towards the rear once I get a sight wheel in my hands, but it is what it is. The recess under the rail may stay as is depending on how it looks when the scope mount arrives. I was using the picture of the assembled rifle to judge where the lower recess ends at the front, it looks like it ends forward of the port door in that photo so that's what I went with. The funny thing is it's also exactly where the radius of the carry handle I cut off ended, makes me wonder if these were forged as is, or A1 forgings were modified before machining on the original 656s? that the final profile of the sight ears?....they appear a bit pronounced... the the ones in the pics of the stripped receiver and complete rifle are more subtle |
| One of the archived threads I found said that they were made by attaching a piece of bar stock to the top of a trimmed down A1 receiver. More or less like you are doing. No source was cited so you can attach as much weight to that as anything you read on the internet. |
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This isn't the mock up anymore, the lower recess will be widened a little towards the top and maybe lengthened a smidge towards the rear once I get a sight wheel in my hands, but it is what it is. The recess under the rail may stay as is depending on how it looks when the scope mount arrives. I was using the picture of the assembled rifle to judge where the lower recess ends at the front, it looks like it ends forward of the port door in that photo so that's what I went with. The funny thing is it's also exactly where the radius of the carry handle I cut off ended, makes me wonder if these were forged as is, or A1 forgings were modified before machining on the original 656s? that the final profile of the sight ears?....they appear a bit pronounced... the the ones in the pics of the stripped receiver and complete rifle are more subtle Agreed. Just a slight reshaping of the forward part of the rear sight ears would have that looking just about spot on. |
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that the final profile of the sight ears?....they appear a bit pronounced... the the ones in the pics of the stripped receiver and complete rifle are more subtle No, they are a little long towards the rear, way too sharp at the front, and a little tall also. I left stock to play with once I get a sight wheel on for reference. The recess under the rail may be cut a little higher depending on how the scope mount fits once I receive it, and the lower recess will be widened towards the top when I machine the good donor receiver and do final fitting to it. |
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that the final profile of the sight ears?....they appear a bit pronounced... the the ones in the pics of the stripped receiver and complete rifle are more subtle No, they are a little long towards the rear, way too sharp at the front, and a little tall also. I left stock to play with once I get a sight wheel on for reference. The recess under the rail may be cut a little higher depending on how the scope mount fits once I receive it, and the lower recess will be widened towards the top when I machine the good donor receiver and do final fitting to it. gotcha..keep up the great work 
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Not that it's any of my business whatsoever, but if I were doing one of those, for the final product I would try to find an A1 receiver with a broken sight ear or otherwise damaged carry handle. Failing that, an NDS-603. That way I wouldn't be cutting up a good, original Colt upper for the project.
Sorry, that's just the cruffler / 03 FFL / history & museum geek part of me talking... preference for leaving original stuff original and all. They aren't rare until bubba makes 'em rare. |
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Not that it's any of my business whatsoever, but if I were doing one of those, for the final product I would try to find an A1 receiver with a broken sight ear or otherwise damaged carry handle. Failing that, an NDS-603. That way I wouldn't be cutting up a good, original Colt upper for the project. Sorry, that's just the cruffler / 03 FFL / history & museum geek part of me talking... preference for leaving original stuff original and all. They aren't rare until bubba makes 'em rare. It isn't up to me, I'm just doing the machining on this project for another member. I agree that an A1 with a bent ear or other carry handle damage would be ideal for the final donor receiver. ETA: I just thought of something, I made the new sight, rail, etc. from 6061. Anybody have any insight on which uppers are 6061? |
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Anybody have any insight on which uppers are 6061? A quick archive search turns up mike_nds saying it was in '68 that Colt switched from 6061 to 7075 (according to the Gun Zone timeline). Ekie also says '68. Early Armalite receivers were 7075, Colt switched to 6061 to save money, then back to 7075 due to corrosion problems in SE Asia. |
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Anybody have any insight on which uppers are 6061? A quick archive search turns up mike_nds saying it was in '68 that Colt switched from 6061 to 7075 (according to the Gun Zone timeline). Ekie also says '68. Early Armalite receivers were 7075, Colt switched to 6061 to save money, then back to 7075 due to corrosion problems in SE Asia. Interesting this came up. I was just reading about the AR development in The Gun by CJ Chivers. He mentioined Colt reps sent to SE Asia found upper receivers eaten through with corrosion around the port door so much the magazine was visible. |
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Not that it's any of my business whatsoever, but if I were doing one of those, for the final product I would try to find an A1 receiver with a broken sight ear or otherwise damaged carry handle. Failing that, an NDS-603. That way I wouldn't be cutting up a good, original Colt upper for the project. Sorry, that's just the cruffler / 03 FFL / history & museum geek part of me talking... preference for leaving original stuff original and all. They aren't rare until bubba makes 'em rare. Just a thought, could a current flat top receiver be used instead, just milling off the rails and adding the new? Ralph |
[ARCHIVED THREAD] - 656 questions (Page 1 of 3)
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