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I used to like watching the $6 Million Man when I was a kid. Your rifle reminded me of that TV show this morning. Xnke, how close are you to the finish line?
 

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Reading through posts like this make me realize just how little I do know! LOL!
I worked in a gun shop for about 2 years. One of the biggest lessons I learned was, "Stop BEFORE you take it apart!"
I'm a "fair to middlin'" Rem 870 mechanic and a somewhat limited Win M12 "tinkerer"!
I'm not sure I could even sweep y'alls shop floors! LOL!
 

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Discussion Starter #24
Thanks for the complements, but truth told...I'm a crap machinist. I just don't get the practice to be "production grade".

I figure I'll have it shooting by march, and finished by may. That assumes I do not find another job and I can't spend money on things.

Right now, I'm missing:

Sight rail / Bolt Hold Open-Material on hand, waiting on 13/64 end mill and 10mm end mill
Barrel-Blank in hand, could start profiling the OD but want to use the new lathe
Muzzle Device-Material on hand, could work on making this tonight
Forward Handguard Hanger-Material on hand, another simple part
Silent Bolt Closing device-Need to obtain an AR forward assist assembly.
Receiver Reinforcing Rails-Material *probably* here, Probably have the tooling too. Gonna be an "interesting" setup to make the radius cuts for the trunnion end.


Need to figure out something to do with the buttstock-the recoil spring lives inside the buttstock, so adding the adjustable cheekrest will be tricky. Adding adjustable LOP is easy though.
 

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Thanks for the complements, but truth told...I'm a crap machinist. I just don't get the practice to be "production grade".

I figure I'll have it shooting by march, and finished by may. That assumes I do not find another job and I can't spend money on things.

Right now, I'm missing:

Sight rail / Bolt Hold Open-Material on hand, waiting on 13/64 end mill and 10mm end mill
Barrel-Blank in hand, could start profiling the OD but want to use the new lathe
Muzzle Device-Material on hand, could work on making this tonight
Forward Handguard Hanger-Material on hand, another simple part
Silent Bolt Closing device-Need to obtain an AR forward assist assembly.
Receiver Reinforcing Rails-Material *probably* here, Probably have the tooling too. Gonna be an "interesting" setup to make the radius cuts for the trunnion end.


Need to figure out something to do with the buttstock-the recoil spring lives inside the buttstock, so adding the adjustable cheekrest will be tricky. Adding adjustable LOP is easy though.
I can help you out with a Forward assist. Send me a PM with your address and I will send you one.
 

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Discussion Starter #27
Thanks to a kind forum member, I have a forward assist coming and can show how I'll adapt the guts out of the AR assist and explain its use for this weapon. I started drawing up the muzzle device this afternoon, as well as the reinforcing rails. Muzzle device won't be difficult, but threading the blind bore is gonna be...interesting...on the Atlas. Leadscrew is a bit worn, but it will still work. I'll have to set up at least 1 dummy run to make sure I do it properly.

Assuming that it goes well, I'll probably make a short run of flash hiders for the 6.8SPC. They will be threaded 5/8-24, if I do, and will be about 2.5" long and 1" OD. I always go for function and fit over form, so it will be what it needs to be to be effective and fit properly.
 

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Discussion Starter #30
the only thing cooler than this would be a STG-44 in 6.8.
And this project is **really** cool.
Thanks for sharing!
It is available if you want one-Contact HMG and get on the waiting list. They already do 5.56 and 300BLK, 6.8 would be nothing to make work in a gas-op rifle.
 

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Discussion Starter #31
Trunnion is now cleaned up and honed straight, 0.7505" all the way through. Here's a test fit shot in the receiver:



I set up and milled out the first operation on the receiver support rails last night. Since the CETME-L is flat-sided instead of cylindrical where the rails mount on, it's a bit easier to make these-but since they're flat, they are also much thicker and heavier than the HK PSG-1/MSG90/HK21e reinforcing rails. I'll have to do some fancy profiling on them to make this thing less suitable for anchoring the USS Iowa.



I can shave them down quite a bit here, the extra stock is for work holding and because it's what I have available. After cutting in the 1.5" radius to slip over the OD of the trunnion end of the receiver, I'll work on how I can slim down the rails so that they're still supportive but weigh less...The original rifle weighed 7.5lbs, I would like this one to come in around 9.5lbs complete.

After milling in the profile, I had to set the plate up on unequal length parallels to cut the taper on the rails. After that, a few quick swipes with a file to radius off the corners, and the rails fit into the grooves nice and tight.



I'll cut the rails free of the base stock after facing off the far side, and probably after I get the radius cut into the forward end of the rail. They are much more stable and less likely to bend right now, but we'll see how it goes.
 

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Discussion Starter #32
First time posting from a phone. Started on the barrel tonight, decided I don't really have to wait on the new lathe, the muzzle threads are the only thing the old Atlas will give trouble with and on a 24 pitch thread it will do OK.

Dialed in the tailstock and set the power feed, 8 minutes 40 per pass, 10 thousandths depth of cut. Taking the barrel blank from 1.250 to 0.750 will take a bit...but, this machine won't run carbide tooling well on something this long and whippy. A good HSS tool, and a few swipes with the slip stone every pass to keep it sharp stops the chatter from starting up, and once chatter starts, it is very hard to get under it and it ruins the finish on the part.

The tooling for the flash hiders showed up today, and the quotes for Melonite treatment. I'll have to make up a batch and see what I can get a batch treated for to know if it's worth Melonite over cerakoat, which I can do in-house.

Once this rifle is done I'll probably do a few more on different actions.
 

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Subscribing as I apparently have missed this thread in the months it has been up and want to see how it turns out. Really good info in here.
 

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Discussion Starter #34
Well, I was doing SO well this evening, I spent the last two days cutting 0.010" per pass off the barrel blank to get it from 1.250" down to 0.751". Got down to 0.775", did the layout for the muzzle threads, main straight section, and then the press fit section that presses into the trunnion. Muzzle thread section turned down to 0.625", main straight 0.730", and then came the press fit shank, that HAS GOT TO BE 0.751". Got into the cut-and-check, shallow passes, getting closer, OK! 0.755" and one more pass to bring it home. And on that last pass, the tiny little flakes coming off, not even enough of a chip to get a curl going, and everything looks great. Except that now the press fit section is 0.750" and is a strong finger push into the trunnion, instead of requiring several tons of press.

Crap.

So, setting it back up in the lathe I get out the old knurling tool and lay a fine diamond knurl onto the barrel. It's now 0.755", and isn't scrap, but I was feelin' so good about getting it all just right, when it all went to crap. Oh well, that's part of why I extended the trunnion. Originally the trunnion was only press fit for 0.8" of barrel length-that's it. Less than an inch of barrel press fit into the receiver, and retained with a pin. Now, it's 3.5" of press fit and still uses the press-fit pin, so barrel support is MUCH more solid now.

I've got another section of barrel that has to be turned down to 0.750" tomorrow and three chambers to cut-two practice chambers, and the real deal. Hopefully tomorrow evening or saturday I'll have both practice chambers done and the real barrel will have the chamber cut, and the muzzle threads finished.
 

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Discussion Starter #35
Started work on the flash suppressors today, made a #3MT to 5/8-24 taper adapter, and cut a few lengths of 1" bar to start. Drilled and threaded 1 blank to fit on the adapter, all machine work will get done on the adapter, so all the machine work is concentric to the threaded bore.

I'm looking at a 3-prong design, with unequal-spaced slots, to minimize dust kickup and flash. I'll have to see if I can find a lightmeter to work with, and do a little flash testing to find what works.

The forward assist parts arrived, and I have started drawing up the forward assist housing/case deflector, I'm left handed/left eyed, so this *very* right handed rifle will just have to deal with it. I'm not gonna be taking hot brass in the face every shot, it's gonna have a case deflector.
 

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Xnke, you passion for this rifle is impressive! It sounds like you have a lot of development ahead of you, e.g., test, fix, repeat. Maybe duplicate the grooves on a known flash-hider and call it good. I enjoy your pictures.
 

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Discussion Starter #37
I got the message today from the gentleman that is providing a HUGE help to this project-The Wizard of Centerville, HolesCreek!

He's been a very active CETME builder over the last few years and developed a method to flute the chambers on a 3-axis CNC mill, instead of the electro-chemical milling method I was working on. (I'm still working on it...but it's early days, man...early days.)

I sent him my chambered barrel and some practice stubs, and he's just sent me a photo of the chamber cast showing the flutes.





It's these thin grooves in the chamber that allow the roller-delayed action to work without just ripping the case head off every time the action opens. Without them, every single shot would be a case head separation.

Once the barrel returns home, I can continue moving forward on this build.
 

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What a great thread. I will be following with lots of interest. Building M1A's and AR's is playing with tonka toys compared to this. Great job so far.



Brandon
 
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