WTK: Collapsible Stock Hard to Open/Shut on Stamped Reciever CETME

[Hoover 1]

And my weekly question for the board experts.:icon_biggrin:

I am trying to put a HK collapsible butt stock on a Century CETME stamped receiver.

I am able to get in on collapsed. It is a very tight fit. When I try to extend the stock, I am not able to.

When I put it on with the stock extended, I can install it. And I can collapse the stock, but can not extend it.

My guess is that the stock rail are hanging up on the receiver rail "stamp" area. It looks like the CETME receiver rail area is "rounded" instead of "square" like on a HK reciever.

I assume that it is a very slight interference and was planning to buffer the upper and lower "rounded" receiver rail area at the rear. Basically make the "rounded" area slightly more square.

Any thoughts/suggestions?

Thanks,

Hoover

[drine]

The round stamping is the issue, you are correct! You'll notice "Blackwing" selling his services of correcting flats in the FOR SALE section. I know that won't do you any good now. Some CETME owners have got these to work so maybe one of them can enlighten us.

[Smokehouse69]

The problem of sending it to BLACKWING is that if he isn't a BATF licensed smith (FFL 07 I think) then you cannot send a firearm to him for work. He can work on a flat and send it back to you but not a completed receiver.

I think that's the rule, but if I am full of crap, please somebody tell me! :D

[bladeworks123]

Both of the things I am about to tell you are very tricky to do on a rifle that is already finished. You will most likely have to refinish the receiver and stand the chance of messing up your receiver.

About the best, (not easiest) way to do this is to use a piece of square bar stock on each side of the receiver and with the bolt carrier in place, press the bar stock into the rails between the jaws of a vice, pressing it in sections starting at the rear, moving the barstock and the bolt carrier forward each time you press. The barstock you use needs to be ground to be a little wider than the retractable arms and as deep, or I've also seen it done with the rectractable arms themselves in place of bar stock. The problem with this technique is that you also need to build shims for the surfaces of the bolt carrier so that you don't squeeze the sides of the receiver in too far and cause clearance problems with the bolt carrier, it will also tend to squeeze in the sides of your magazine well and require you to tweak it again to get it right. This is alot easier to do when building a rifle instead of doing it to one that is already finished. This will square up the rails and shape them to fit the contours of your bolt carrier and let the retractable stock have room to work. You will marr the finish of the rifle doing this.

Another method is to use a round cylinder diamond burr in a dremel tool to widen and deepen the receiver rail grooves. This works if the arms lack only just a little bit of fitting correctly. I almost hesitate to mention this method because you have to be extremely careful not to remove too much metal, as you can weaken the receiver by making it too thin in the area of the rails.

The best option might be to consider putting a side folder stock on. If you haven't shot the Cetme or HK91 with the retractable stock yet, it only takes one or two rounds to discover why they are nicknamed "meat grinders". They look cool, and make the rifle nice and compact, but they will pound the HE double toothpicks out of your shoulder and cheek bone. The side folders are a lot more comfortable to shoot.

[SSwee]

Here's a pic of a PTR receiver and 3 flats I squared the rails on. One after it was bent and welded and two while still flats. I used a 4" piece of 1/4" x 2" flat bar that I ground to fit the PTR rails, an old stripped carrier and a 4oz ball peen hammer. I worked the rail a little at a time, back and forth to get it even. One side then the other with a two by four for a back plate. As bladeworks mentioned it may tweak the receiver in other area and will definitely not good on a finish.
SS

[patjsimpson]

SSwee,

It would be great if you could put up a short tutorial on how to do this with a a few more pictures. I am sure smomeone would stick it to the top. This is one of the things I see asked about alot. I myself kind of get what you are describing but would want to to get a better understanding before I went to work on an $80 flat if you know what I mean ;-) Not quite that confident in my capabilites!

Thanks!
pat

[SSwee]

I'll get some more pics tomorrow.
SS

[Hoover 1]

Both of the things I am about to tell you are very tricky to do on a rifle that is already finished. You will most likely have to refinish the receiver and stand the chance of messing up your receiver.

The best option might be to consider putting a side folder stock on. If you haven't shot the Cetme or HK91 with the retractable stock yet, it only takes one or two rounds to discover why they are nicknamed "meat grinders". They look cool, and make the rifle nice and compact, but they will pound the HE double toothpicks out of your shoulder and cheek bone. The side folders are a lot more comfortable to shoot.

That is what I was afraid of.

I may just go with the Choate side folding stock and put the G3 collapsible stock away for a future project.

Thanks,

Hoover

[drine]

The problem of sending it to BLACKWING is that if he isn't a BATF licensed smith (FFL 07 I think) then you cannot send a firearm to him for work. He can work on a flat and send it back to you but not a completed receiver.

I think that's the rule, but if I am full of crap, please somebody tell me! :D

Correct. His services are for flats so OK with BATFE. It won't do HOOVER1 any good, just illustrating the rounds vs. square groove issue.

[earls]

I had the same issue when I installed the collapsible stock on my Century Cetme.
I installed the stock collapsed and worked the rails with a dead blow hammer to get the clearance needed. I did this slowly and progressively until it slid freely.
I also kept a constant check on the bolt operation and had to tweak the receiver a few times to get everything to work properly. When my bolt carrier would start to bind / hang I would hold the receiver in one hand and tap down on the top to re-open the side rails. It took me about 20-25 mins to get it working properly. This also didn't destroy MY finish, just some light marks (which may have been from sliding it when it was tight).
If anyone were to do this I would caution you to be careful and not try to get it working all at once. Take your time.
Earl

[bladeworks123]

That is what I was afraid of.

I may just go with the Choate side folding stock and put the G3 collapsible stock away for a future project.

Thanks,

Hoover

FYI.....I see that RTG just got in the HK contract Choate side folders.

[david sarnoff]

adjustable for length of pull.

http://www.riflestock.com/catalog_page_detail.cfm?recordno=4&Product_CatalogID=2966&ProductNumber=15-01-12&ProductCode=32&ProductSubCodeID=196&NewProduct=0

[Hoover 1]

adjustable for length of pull.

http://www.riflestock.com/catalog_page_detail.cfm?recordno=4&Product_CatalogID=2966&ProductNumber=15-01-12&ProductCode=32&ProductSubCodeID=196&NewProduct=0

Yeah, I was looking at the Choate adjustable stock on HKparts.com.

http://www.hkparts.net/shop/pc/viewPrd.asp?idproduct=884&idcategory=9

They are going for $100, so I will probably pick up one of these when I can.

Thanks,

Hoover

[Hoover 1]

I had the same issue when I installed the collapsible stock on my Century Cetme.
I installed the stock collapsed and worked the rails with a dead blow hammer to get the clearance needed. I did this slowly and progressively until it slid freely.
I also kept a constant check on the bolt operation and had to tweak the receiver a few times to get everything to work properly. When my bolt carrier would start to bind / hang I would hold the receiver in one hand and tap down on the top to re-open the side rails. It took me about 20-25 mins to get it working properly. This also didn't destroy MY finish, just some light marks (which may have been from sliding it when it was tight).
If anyone were to do this I would caution you to be careful and not try to get it working all at once. Take your time.
Earl

Or I may just go Bubba on the stock and make it work.:thumbup:

Seriously, the interference that I am seeing is pretty slight since I can collapse the stock but just can not get the leverage to extend the stock.:icon_biggrin:

Thanks,

Hoover

[SSwee]

Hoover,
Just for you and my own curiosity I used the same technic on my CAI Cetme.
Turned out good. Give me a few to DL pics off the camera and peck some keys.
SS

[Hoover 1]

Hoover,
Just for you and my own curiosity I used the same technic on my CAI Cetme.
Turned out good. Give me a few to DL pics off the camera and peck some keys.
SS


SSwee,

I would appreciate the photos.

Without the help of the members on this site, my CETME would have been sold long ago.

Thanks,

Hoover

[SSwee]

<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 9"><meta name="Originator" content="Microsoft Word 9"><link rel="File-List" href="file:///C:/DOCUME%7E1/Owner/LOCALS%7E1/Temp/msoclip1/01/clip_filelist.xml"><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:DoNotOptimizeForBrowser/> </w:WordDocument> </xml><![endif]--><style> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> </style> Squaring CAI Cetme rails using basic metal working skills. I took a 4” piece of ¼” x 2” flat bar and tapered one of the 4” sides from .210” on the edge to .250” an inch up. This can be done with a file or belt sander since it is only taking .020”off of each side. It just needs to be as even as possible. I used a 4oz ball peen hammer and a carrier with the bolt head, LP, and firing pin removed. The carrier was inserted in reverse with the edge of the carrier main body flush with the rear of the receiver. I set this set up on a 2x4 on a solid surface to work. I used solid strikes to the flat bar keeping the strikes over the carrier main body and working down the receiver moving the carrier approximately half the length of the carrier main body. This was repeated on the other side. The rails should be squared up now.
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After squaring the rails, the receiver will be too tight for the carrier to slide freely. A couple of squeezes in a vise or press will free up the carrier. I had to press the receiver vertically where the trigger box mounts with a 1x2 in place of the trigger box and behind the trunnion pressing on the shelf block that holds the trigger box up. The last thing I had to do was squeeze the receiver back together where the trigger box mounts. I put the carrier in the receiver centering it where the trigger box mounts. Using the ball peen hammer and a piece of 1x2, I set the edge of the 1x2 where the trigger box normally rests against the receiver and gave it a couple of good strikes on each side of the receiver to take a slight bow out that prevented the trigger box from going into position.
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Reassembled and checked for function. The only real scuffing to the finish was the lines in the rail.
If your up to it, PM me with an address and I'll send the tool I made to square the rails. Its done 7 receivers already but should be able to get a few more before it's wasted.
SS

[Hoover 1]

SSwee,

Excellent information.

PM sent.

Thanks,

Hoover

[Smokehouse69]

Great post SSwee! :thumbup:

[Hoover 1]

Big thanks to SSwee for the rail wedge!!:rockon:

I modified the process slightly to include a thin shim between the bolt carrier and the ID of the receiver.

I "squared up" only the rear of the receiver at this point.

Fit up of the stock and test fire will occur over the next few days, provided that work, wife, kid, etc, etc allow.:wink:

Thanks again to SSwee.

Thanks,

Hoover

[KidKalash66]

Gee,I thought "I" invented this process,heh heh. I did the above in those excellent pictorials(thanks!)to my early Hesse home build 91 in order to get the fixed stock to slide off and on better.What's cool is that after squaring the channels into the carrier grooves,I discovered my charging handle unlocked even easier,and the slightly crunchy spring noise of charging became as smooth sounding as working the slide of an old Winchester Mod12! The ejection even became more uniform,to the front at 1:00 in a tidy pile. THEN I put a retractable stock on it a few weeks later,fit like a glove. But I hated the ergonomics,like laying your head on a rail and waiting for the 6:10 Southern Pacific to come along and decapitate you! I guess Paratroopers have more than jumping out of a perfectly good airplane to gripe about! :nonono:

[k98k792]

Great thread! Stuck it is!

[h&ktexan78]

I attached a HK collapsible stock on my CETME Sporter and had somewhat the same problem. It was very stiff at first extending and collapsing. All I did was played with it for 30 mins or so closing and extending over and over and it finally became quite easy to operate. I didn't do anything else to it. At first I was worried about it scratching the finish on the receiver but it didn't. I do have to say though that it was very uncomfortable to shoot so I took it off and put the HK stock back on it. It looked very cool and was more easily stored or transported but that was the only advantage that I could see.

[mitchstoner]

Great info, and very timely as I am gathering info before starting my first CETME build, from a flat.

Couple of questions: Anything I should do significantly different from SSwee's process if I square the rails on the flat before bending?

Second, if I use a carrier that I'm planning to put into a build, will there be any possibility of damage to it?

(btw, a few years ago I bought a PTR-91 with the collapsible stock, and sure wish I had saved the extra cash and ordered it with the fixed stock. Hate shooting it with the collapsible. But yes, it looks cool.)

[bladeworks123]

I don't know if I would do the rails before I bent the flat... The only reason I say that is, that you are going to have to do a little tweaking after you bend it anyway. I found on my second build that the act of forming the rails with the carrier seemed to solve a lot of other fit issues, like correct width and height of the receiver. Also, I think if you were to try correcting the rails before you bent the flat that you would have to build a jig that would keep you from flattening out the sides of the receiver more than they already are, or you might have more problems getting the receiver to roll to the right dimensions. If you aren't going to build from a flat that has already had the rails corrected, I would use Sswee's method.

[SSwee]

I used the same method on flats before bent and after bent/welded. I did not notice one way being better than the other. Each had little quirks to deal with but nothing major.
SS

[texlurch]

If you'll notice on the "new" style collapsible stocks, the curve on the butt is just the opposite of normal. It puts all the recoil into a small spot of your shoulder. They were designed so you could put them on the ground easier when launching grenades.

I have a couple of the old style "French curve" collapsible stocks that mimic the normal curve, and they are just fine to shoot. Very hard to find tho... :)

This is my HK51 clone, CETME receiver, 16" barrel, fake can.

[FullAssault]

I just put a collapsible stock on my Cetme also. It slides in and out fine but sometimes it gets stiff and pops then it's easy again. I've looked it over and over and I'm not sure what's going on. I like how this stock is easy to put on and take off vs the norm HK stock. I don't think it's that bad when shooting but I shoot alot of 8mm and 54R surplus guns.

http://img404.imageshack.us/img404/4374/cetmea42.jpg

[teknotronik]

That is exactly what I want to do with the collapsable stock and quad rail setup. Was it really that bad?


I attached a HK collapsible stock on my CETME Sporter and had somewhat the same problem. It was very stiff at first extending and collapsing. All I did was played with it for 30 mins or so closing and extending over and over and it finally became quite easy to operate. I didn't do anything else to it. At first I was worried about it scratching the finish on the receiver but it didn't. I do have to say though that it was very uncomfortable to shoot so I took it off and put the HK stock back on it. It looked very cool and was more easily stored or transported but that was the only advantage that I could see.

[jfowl31]

I realize this might just be band-aiding the problem and I don't have a collapsible stock in front of me, but could you just round the corners on the stock that bind on the receiver? Would that make the stock loose when extended?

I've never really paid attention to where the stocks lock in place to know if rounding the corners would make everything loose, but it seems like much less work if the only end result needed is to make a collapsible stock fit and slide smoothly.

[Hoover 1]

I just put a collapsible stock on my Cetme also. It slides in and out fine but sometimes it gets stiff and pops then it's easy again. I've looked it over and over and I'm not sure what's going on. I like how this stock is easy to put on and take off vs the norm HK stock. I don't think it's that bad when shooting but I shoot alot of 8mm and 54R surplus guns.

http://img404.imageshack.us/img404/4374/cetmea42.jpg

Nice looking set up.

I had one on a CETME and it was really not too comfortable to shoot.:icon_cry: I have since switched back to a standard stock.

Thanks,

Hoover

[SteelCore]

+1 on the Choate side-folder. Nice folders, they are.