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Just registered here, didn't even know this place existed till this evening. Been working on a CETME-L build for about six months now, only reason it didn't get done in a week is that I'm not building it in the original 5.56x45 caliber-Mine will be the only one in the world chambered in 6.8SPC.

So what is the CETME-L? It's the old Spanish service rifle, that was replaced with the HK G36. (which both Spain and Germany dislike now...) Originally the reasons for dropping the rifle were that it malfunctioned...this was due mostly to junk magazines and poor quality springs. Earlier production rifles and mags were generally fine, but later, cheaper production rifles and mags tended to not work so well. But, since the -L model used STANAG magazines, any AR/M16 magazine would work fine and actually improved the reliability and function of the weapon. (Just don't get caught using a non-issue mag!)

I bought my parts kit and flat about two years ago, back when Armory Parts Exchange had them for sale. They have since sold all the rest of their kits to a single builder in Ohio, so unless you already have a parts kit, this will be even less easy to duplicate. That said, I'm building this:





My Cetme-L semi-automatic variant:

18" barrel length
Replacing iron sights (the spanish sights are terrible) with a Picatinny rail on the receiver
6.8 SPC chambering

Now, when you build a rifle from a parts kit that was or would be banned from importation, you are required to follow a set of laws commonly referred to as "18 USC, Chapter 44, Section 922r". Basically, once a receiver is built as a machinegun, it'll always be a machinegun, so the receiver has to be destroyed on importation. In addition, the new receiver must be considered not readily convertible to full-auto, so some full-auto denial measures have to be taken to prevent use of fully-automatic enabling parts. On top of all of this, you may not use more than 10 imported parts (or parts made from imported parts) out of a specific list of 20 types of parts when you build it. Once you use those 10, you must use USA-Made parts to make up the rest of them. Parts you make yourself, from scratch, are considered USA-Made parts, as well as USA-made parts sold by vendors. Parts you modify from original imported parts are NOT USA-made, and can get you in trouble.

So, part of the reason for building my 6.8SPC variant is because I have to make a bunch of parts anyway, so why not?

The "bad parts" are the following:

  1. Frame, receiver, receiver casting, forging or stamping
  2. Barrel
  3. Barrel extension
  4. Operating rod
  5. Gas piston
  6. Forearm or handguard
  7. Mounting blocks (trunnion)
  8. Muzzle attachment
  9. Bolt
  10. Bolt carrier
  1. Trigger
  2. Trigger housing
  3. Hammer
  4. Sear
  5. Disconnector
  6. Buttstock
  7. Pistol grip
  8. Magazine body
  9. Follower
  10. Floorplate
So, from that list, I see that my rifle does not have a Gas Piston, Disconnector, or Barrel Extension, so only 17 parts-that means 7 or more have to be US made. I chose to make the Receiver, Barrel, Sear, Muzzle Device, Magazine Body, Follower, and Floorplate. This will let me use all the remaining parts of the kit, no problems. I already gotta change the barrel, and the magazine (one mag has 3 parts that count!) so why not change the caliber, making it impossible to use original imported mags.

First things first, the bolt face. It barely has enough meat to open up to the 6.8 base size, so there is no going to 7.62x39 or larger...this is as big as it gets.

Original Bolt Face:


Modified Bolt Face:


Alright, case fits!


Next on the list is magazines. ASC makes a decent one, mine fit and feed just fine. They are so light compared to an original CETME-L mag, too! In the future, I may work out a way to modify an old CETME 12-round mag body to work, but I'll have to replace a handguard/buttstock/pistol grip part if I want to do that. For now, the handguard is going to change-I am not so keen on the one that came in my kit.

After the bolt face was modified and I saw it would work fine, and I worked out a mag solution, I started on the receiver flat. I used an HMG flat, which, they're expensive but they are very nicely made. Once the flat is laser-etched with my serial number and cartridge information, my personal logo, and my maker's mark, it was bent into the proper shape.

I've got the buttstock slipped onto the rear, and the front trunnion inserted into the front. The flat is being lightly clamped in the vice here, just tight enough to hold it together while I tack weld it.



You can see the weld mark where I installed and welded the full-auto denial bar into the flat. It prevents the use of an un-modified full-auto trigger group.

Here's the rear of the magwell, a solid steel milled bit that holds the front of the trigger group in with a pin, and the magazine release plunger.



All welded up! Some cleanup was done with a file, but not much was needed. TIG welding is the way to go here, you do NOT want to deal with burning through the flat and having to work inside the thing with a file and sandpaper just to get the guts to fit.





I did have to adjust the length of the receiver slightly. It is too long, and the stock won't line up with the pin holes that hold the stock on.



Because this is a roller-delayed rifle, instead of a gas-operated rifle, adjustments for different cartridges aren't so easy. I had to make a new locking piece. The original locking piece has a 52 degree angle ground into the sides, and after working out the differences in bolt thrust I determined I will need something between 38 and 46 degrees. A lower angle makes the bolt slower to unlock, but a bolt that unlocks too fast tends to batter the rifle to bits in a very short time, if it's not so fast that it literally rips the casehead off the case and spews burning powder into your face. I rather would like to avoid that, so I made this jig and a stack of locking piece blanks:



After the blanks are turned and milled, they're locked into this jig and the angles are ground in. With no wedges under the block, it will cut a 40* locking piece, which is where I will start-it *should* be the correct angle. Unfortunately, there is very little data to work with for this rifle, I had to borrow a LOT of data from the HK-built versions of this type of action, the G3/HK91/HK93/HK33. Many sporter models and alternate cartridge models of those exist so there is data aplenty to work with.
 

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Discussion Starter #2
Now, like all roller-delayed rifle actions, the CETME-L has a fluted chamber. Internal grooves, that run from just infront of the case mouth, about 80% of the length of the cartridge wall. This acts to "float" the front part of the case on propellant gas, leaving only the rearmost part of the case sealing the chamber and allowing the rifle to cycle without ripping the casehead off with the extractor. If you do not have the flutes, or they are not cut correctly, it WILL eat cases. It WILL cram multiple cases into the chamber, and it WILL ruin your day. but, while they seem to be a trade secret, they aren't...these are hammer-forged in during manufacture, Sinker EDM-cut, or ECM cut. Individuals have cut them with triangular files, scrapers, single-point tooling on a CNC mill, lots of ways...I will either single-point them on the mill, or build a ECM station to electrochemically cut them.

This is an original barrel split through the chamber section, showing the fluting:



The original barrel is pretty dang thin too, so I'll be upping the OD on mine...mine can be heavier, as I am not packing it all day.

Section Cut through the front sight block area:



And the whole thing:



You can see the barrel pin doesn't leave much room for a bigger case-there is more than enough there but going to a larger diameter case than 6.8 is asking for trouble during barrel pinning. I forsee needing to clean up the chamber with the reamer and re-cut the flutes in the part of the area near the pin, after the barrel is pinned into the trunnion. I'm boring the trunnion some to increase my barrel diameter to help with that. (also, since the barrel presses into the rear of the trunnion, the maximum barrel diameter is what will fit through the trunnion...)

Now, next on the list of parts to make is a set of reciever reinforcing rails, as was used on the HK PSG-1 and MSG-90 marksman's rifles. I am still considering the forward assist addition and I am already committed to both the optics rail and to the fully-floating barrel, so I don't see any reason to stop there...mine will get the T-rails too.



It will be a long time finishing this thing up, as my day job (in a large machine shop) is really eating a lot of my time lately. Big projects mean strict deadlines, and for a process engineer it means hitting the floor at 3AM and going in early to get a jump on the job. On top of that, my homebuilt ECM machine project hasn't been going too great yet, I managed to achieve a mirror finish on some parts but nothing as complex as the chamber fluting...YET.
 

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Neat project, Xnke! I'm impressed. Thanks for sharing. Looking forward to seeing the final product.
 

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Have three CETME 7.62×51's and whenever find one with bolt gap in spec and rollers in good condition will add it to the pile. Fine poor man's G3 and can beat the crap out of them and let the G3's sit as vault queens. Good luck and keep us updated. I have passed up some CETME-L kits and quite a few complete rifles cheap as have no use for a baby CETME but you sir may have me picking up next parts kits or rifles I run across at fair price.
 

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Always wondered why the chambers were fluted in the HK. Now I know! Thanks for the insightful posts of your project.

Over time the locking rollers need to be oversized if I understand correctly. I have a CA registered preban HK91 with roller marks on the receiver because of this. The largest oversized rollers were recommended before pressing out the roller marks.

Still haven't got that done because of the ****ty laws in CA mandating out of state shipping requires going through a licensed assault weapon dealer. Shipping out of CA isn't the problem, but getting it back would not be possible if not done correctly. Not many licensed AW dealers in CA and zero in NorCal.

Might check if upsizing the rollers on your build would make sense.

I'll be watching your build progress!
 

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What a wonderful project and running updates. AND...pics, with intelligent descriptions.

Thank You very much...........your project will indeed be one of a kind. Please continue to post progress.
 

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Discussion Starter #13
Been a bit since I posted about this-I lost my job due to cutbacks at work, so I've been busy hunting a new job and keeping the bills paid until then. Also, the PTG chamber reamer should show up sometime this coming week, so hopefully I can put some more time into this.

In the meantime, I've been working on the new forearm, it's on the 3d printer right now. Once finished I'll slick it up and use it to create a silicone mold, and I'll pour a resin "mold master" to make a set of production molds from, if I get enough interest from folks who want US-made parts for these.



There are two lightening/air-space holes drilled the length of the part, as well as the air-space gaps in the main channel where the steel heat shield fits. If this shape fits the hand good, but feels like it needs more "grippy" added to it, some longitudinal grooves may be added before making a mold. I'm also looking at adding a flat mounting plate integrated into the forearm to mount a bipod on, but for now the initial proof of the model data will be enough to deal with.

T-rails are on the list for this coming week too, I'll make and fit the T-rails for the receiver, and maybe (if I can find enough clamps) I'll get the optics rail machined out as well.
 

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So while waiting on the forearm to print, I set up and cut out a combo bolt hold open/scope rail. Shoulda dug out the old Picatinny rail print but instead I cut it from memory, and due to being sloppy one end of the rail is 0.003" undersize. The Warne scope rings fit OK, but since I didn't have the correct numbers in my head, I'll probably start over and do another. Also using a 90* slot drill instead of a regular end mill and some questionable V-blocks would help, but it is what it is. I have not cut the cross-slots yet due to not having the proper size end mill.



Forearm had a print failure this morning, 10 hours into the print...



It's running again, and will be read for me to finish and file-fit to perfection Tuesday.
 

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Xnke, looks like you are having fun. Thanks for keeping us updated on your progress.
 

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Had some issues with the printer not finishing the print, so fired one off in "draft quality". Finished in 13 hours, and while it's totally unusable as a mold master, it's good enough to proof the model and allow me to make adjustments.



There are some minor things I'll have to address in the model, and then I'll have to fit the dowel pins that will leave the holes for the brass threaded inserts to fit into when the mold is poured.
 

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Well, anything that launches brass in to low earth orbit is a pain to reload for, but with a brass catcher there's nothing wrong with the brass out of my other roller delayed actions.

People think the fluted chamber causes the cases to be non-reloadable...they're very wrong. There's nothing at all wrong with reloading fluted chamber cases...if you can find them. The flutes in a properly functioning Vorgrimmler chamber do not cause any reshaping of the brass, it's just soot marks down the side of the case. They can be stubborn to remove, but if you're actually getting brass extruded into the fluting, then you probably have cases that have the extractor rim ripped off, too. If the flutes are cut too wide or too deep, then the brass extrudes down into them and causes much bigger issues than reloadability.
 

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Mangled that almost-finished scope rail/bolt hold open the other day. Gonna have to start over on that-I can save the rail but the bolt hold open is not economical to repair.

Chambered a dummy barrel stub tonight and worked out what my barrel dimensions need to be to press into the trunnion, and work out my press depth. Unlike an HK or the earlier CETME-C rifles, these have a lip cut on the rear of the barrel that *should* press flush against the reciever-no press-and-pray fitting work. That only works if you KNOW the press distance for this trunnion/bolt head combination, so the dummy is a slip fit in the trunnion, with a complete chamber cut. I'll also be using this one for a chamber fluting practice run, and I have a second one made up for more practice-also to break in the chamber reamer. Sometimes a brand new chamber reamer is just *too sharp*, and wants to grab and chatter until it's cut a few chambers-I always go at least two chambers before using a new reamer on an actual barrel.

By the end of tonight, I'll have the extended trunnion finished up, ala PSG1/MSG90A style rifles. I could start profiling the barrel but I really want to get the Logan up off the floor and do the barrel work on it. The Logan lathe is in better condition all the way around than my old Atlas, and will leave a much nicer finish on the turned barrel. Which would be important if I was going to blue the barrel, but since I'm going to be duracoating the rifle, it doesn't matter that much-the whole thing will have to be blasted before coating.
 

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Trunnion welded up nicely, and it seems to be something similar to 4130 steel. Welded to the mild steel extension very nicely, and even though I burned through into the (pre-reamed) bore in a few tiny spots, it didn't harden up appreciably harder. To weld it, I set it on a block of wood in a plastic dish of water, up to right behind the barrel pin hole, and put it in the freezer until completely frozen. Once frozen, I welded fast, hot, and in a hurry, and the by the time the last dime was layed the ice had only melted back just barely enough to slide it off the back of the trunnion. A quick check with the hardness file set and it's still between RC40 and RC45 until right on the weld, which is RC50 to RC55. A good US made file will JUST cut it where the weld is, but carbide tooling (Even in the old Atlas) made quick, but ugly work of it.

Since my 3/4" reamer is carbide tipped, and it's an old reground one at that, AND one of the carbide tips already has a tiny nick in it, I ran the reamer through using a boring bar holder and the power feed, and it went through with no trouble at all. You could definitely tell when I was cutting trunnion, weld, and the mild steel extension though-the reamer cut 0.7495" through the trunnion and weld and the lathe loaded up enough to slip the (admittedly 50 year old) belt, and cut 0.7505 through the mild steel section like it wasn't doing any work at all. I'll have to run a brake hone through a few swipes and even that out a bit, or it could make pressing the barrel in a tough job.

The trunnion extension brings the support for the barrel forward another 60mm, so the total supported length of the barrel is now 80mm. I'm contemplating trimming the extension back a bit, maybe 25mm or so, because the cartridge case isn't that long, and the barrel only really needs that extra support to about an inch beyond the chamber.

Up next on the extension is milling a little off the flat surface on the top, so I can get the cocking tube to drop down low enough. I am going to split the difference though, and remove most of the metal from the cocking tube with a belt sander and the cocking tube will weld to the top of the trunnion extension as well as the receiver-this should improve the stability of the trunnion as much as adding the T-rails on the side will. The rear of the handguard will have a screw that threads up into the trunnion extension, and the front of the handguard will have a cross pin that pins through the front of the cocking tube as per a normal CETME-L, but instead of a front sight base, a plane jane bit of steel tube will be welded on and capped off. This thing has enough metal hanging out the front already!

I have decided that a 20" barrel may be a bit too much-my blank will do a 24" barrel but I think 18" plus 2.5" of flash hider will be plenty, and 20" plus 2.5" of flash hider might be getting a bit long, since the barrel will be limited to 0.750". I don't want it to get TOOO whippy out there....
 
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