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Cobray M11/7.62x25


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#1 Gunfixr

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Posted 27 June 2008 - 01:34 AM

As I've alluded to elsewhere, I'm building a Cobray M11/9mm kit, only I'm building it in 7.62x25 Tokarev.

The kit came with everything to build a 9mm semiauto Cobray except the center piece of the lower receiver.

Since the 7.62x25 round is quite a bit longer than 9mm is, I can't use the mags. I've acquired CZ26 32rd. stick mags, and a PPSh41 barrel, the case rim is basically the same diameter, and the muzzle energy is similar, so the bolt and recoil spring should interchange. I have made the center section and welded the lower together. I have cut and lengthened the magwell to take the CZ26 magazine, and I have turned the barrel to screw into the M11 upper the same as the original barrel did. Where the 9mm barrel is about 5 1/2" long, the PPSh barrel is 10" long. I'm going to leave it, for maximum velocity, and make and weld onto the upper an extension, kind of like a square barrel shroud, with the same basic profile of the upper, having cooling slots on the sides at least. I'll move the front sight out to the end of this extension, and put a rail behind it in front of the cocking handle. I may put rails on the sides and bottom as well, we'll see. A sling loop on the back will complete the package.

I'll be taking pics as it goes to show the progress.

As I'm not a manufacturer, it won't be for sale.
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#2 acer_saiga308

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Posted 27 June 2008 - 06:49 AM

Sounds pretty interesting. Looking forward to the pics.

Keep us posted,
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#3 THE_HUNTER

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Posted 27 June 2008 - 05:29 PM

Great round! :smoke:

#4 Gunfixr

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Posted 02 July 2008 - 05:39 PM

Things are coming along nicely on the build, and I've got some pics.
This first one is the kit layed out. I've cut open the magwell, rebent the front to make it longer, and cut the piece to weld in and close it back up. Also, I've made the receiver center section. The CZ26 mag is shown beside the original for size comparison. Also, the original and PPSH barrels are shown, as are the two cartridges.
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In this pic, the barrel has been turned to fit the M11 upper, and the receiver and magwell have been welded up.
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In this pic, the trigger guard, which is also the feedramp, and the magwell have been welded onto the lower receiver. Also, it can be seen how the barrel fits to the upper.
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In the final pic, pretty much the whole gun is assembled, it's missing only the hammer and firing pin. All part fitting is complete, and the feedramp adjusted and magazine catch and magazine modified. When rounds are put in the magazine, and the action hand cycled, they feed and eject perfectly. I actually lost one somewhere in the shed when it ejected to a far corner and landed behind something. It still needs a little final finishing, but it's in working order.
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I've also decided to change what I was going to do to cover the long barrel. Instead of fabricating a squared receiver extension, I'm going to make a round one that will look like a supressor, but be semi permanently attached to the barrel. I think it'll look much better that way.
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#5 moxie1c

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Posted 02 July 2008 - 09:54 PM

drool. Tony should make one for us in 7.62 :devil:

#6 Thumbhole

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Posted 02 July 2008 - 10:37 PM

Nice work! Now, go make a 7.62x39 belt fed upper for my M11! Nevermind, it's been done and was declared a post 86 machine gun.

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Why do the 7.62x25 besides the cool factor? It is cool! Any other benefits?
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#7 Revelation

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Posted 02 July 2008 - 11:07 PM

Awesome job!

#8 MD_Willington

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Posted 03 July 2008 - 10:57 AM

7.62x25, while being cheap, it is also a pretty potent round.

Great job on the conversion!
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#9 THE_HUNTER

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Posted 03 July 2008 - 11:06 AM

7.62X25 penetrates extremely well and out of my CZ52 will shoot through steel waterproof ship doors that will only be dented by a .357mag! Oh yeah, punches through level 2 kevlar.

#10 Gunfixr

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Posted 04 July 2008 - 01:01 AM

Yeah, it punches a lot, and JHPs are also available. I'm sure they'll open right up at those velocities.

I got the sling mount on the back, and the barrel shround mostly done. It's not threaded, and the barrel threaded yet. I'm also going to make a taller cocking knob, reminiscent of the original M10s.

Another benefit is ammo price. I just ordered 1000 rounds, and it was $126, shipped to my door.
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#11 THE_HUNTER

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Posted 08 July 2008 - 07:28 PM

Sweet toy!Lucky you are handier than I for sure.I just by stuff,can't make em...... ;)

#12 Gunfixr

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Posted 09 July 2008 - 12:03 AM

Here's the latest pic. It's assembled and fitted, ready for test firing. The barrel is screwed into the upper and then pinned to lock it. I haven't pinned it yet in case I need to change the headspacing a little. Once it's test fired and working properly, I'll pin the barrel and Duracoat it.

Posted Image
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#13 THE_HUNTER

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Posted 09 July 2008 - 04:14 PM

That is so awesome and one of a kind! :super: I am envious to the 1000th degree!

#14 Gunfixr

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Posted 14 July 2008 - 10:11 AM

Took it to the range yesterday. Had some problems. One, the action of the Cobray is too weak to reliably fire the rounds. Since mostly they are "subgun" rounds, their primers are rather hard. I'm not getting good primer indentation. It has a light firing pin with a heavy spring that is also an inertia pin. I'm going to make a new direct contact pin and retry. Second, the bolt is opening just a tad early. It's not bulging or blowing out the cases, but the neck is bulging out, and it's blowing a lot of soot back into the action. Since it has about an inch of unused bolt travel, I'm going to put a spacer on the recoil spring guide, which will tighten up the spring some. This should about do it. If not, I can weight the bolt down some.


I only got a handful of rounds to fire, but it's pretty cool. It really cracks when it goes off, and with the dummy supressor, there's no muzzle flip.
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#15 Gunfixr

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Posted 17 July 2008 - 02:05 PM

Back to the range today after making new firing pins and shortening up the recoil springs some.

Much better, fires fine now, but still needs a bit more tweaking. Some rounds still failed to go off, but it was just a few out of the 150 or so rounds fired. The ones that didn't go off had good indentations and failed to go off after repeated hits, so I think they are just bad rounds. Had to tweak the mags a little to get good feeding. It still needs the bolt speed reduced a little, I'm going to add a little weight to the bolt. The main problem now seems to be the ammo. The consistency os way off. There is a noticeable difference in the power of the rounds, either due to age, or just loaded bad to begin with. I think the next ammo I get in this caliber will be the Romainian, maybe it will be better.
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#16 AgentLQ

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Posted 17 July 2008 - 04:04 PM

That is straight dope man! :super_man:

Enjoy some relatively cheap plinking for me would ya?
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#17 THE_HUNTER

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Posted 18 July 2008 - 04:31 PM

Great news! Try some Winchester Metric 7.62X25 to see it work perfectly for sure. Great rounds! I got a bunch for my CZ52 years back for $9.99 per 50. :super: Reloadable boxer primed too! :up: Sucks trying to find them in the grass as my pistol sure wings em far over my right shoulder.

#18 Knuckle Dragger

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Posted 19 July 2008 - 12:12 PM

Gunfixr,
Do you have a CZ52 or TT-33 to test the "bad" rounds in? If the com-blocs don't fire the primer, than you can feel safe knowing the rounds are bad. If they do, we'll then that can only help in the "tweaking" process.



Back to the range today after making new firing pins and shortening up the recoil springs some.

Much better, fires fine now, but still needs a bit more tweaking. Some rounds still failed to go off, but it was just a few out of the 150 or so rounds fired. The ones that didn't go off had good indentations and failed to go off after repeated hits, so I think they are just bad rounds. Had to tweak the mags a little to get good feeding. It still needs the bolt speed reduced a little, I'm going to add a little weight to the bolt. The main problem now seems to be the ammo. The consistency os way off. There is a noticeable difference in the power of the rounds, either due to age, or just loaded bad to begin with. I think the next ammo I get in this caliber will be the Romainian, maybe it will be better.



#19 Gunfixr

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Posted 20 July 2008 - 04:27 PM

Don't have a CZ52 yet, but working on it. I was figuring the same thing, try to fire the "bad" rounds in the ComBloc gun and see what happens.
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#20 Gunfixr

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Posted 13 August 2008 - 11:14 PM

Finally picked up a CZ52 pistol, so I'll be able to compare the Czech ammo in it to the Cobray I built. It'll take a few days, I gotta clean out the cosmoline first. The Cobrays are torn down for blasting and Duracoating, have been for over a week, but just too busy to get them done.

Also got a can of 1224 rounds of Romanian ammo, dated 1982. Looks much nicer than the 1951 Czech stuff. Haven't fired any yet.
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#21 Gunfixr

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Posted 21 August 2008 - 09:03 PM

Well, the CZ52 shoots the old Czech ammo much more reliably than the Cobrays do, so I know they need a little improvement, unless the Romanian is more reliable. Still haven't got them Duracoated yet.

Made a better steel, spring loaded firing pin for it. Also converted it from the European mag release to a push button mag release behind the trigger guard.
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#22 Gunfixr

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Posted 13 September 2008 - 11:24 AM

Finally got the Cobray finished, sat around for weeks waiting for an opportunity to Duracoat them. Got them done, did the inside as well, to help protect against the corrosiveness of the ammo. Took it to the range and ran about 150 rounds through it, as it "broke in" it got better. Working good now. The empties eject about 15-20 ft. away. The strap on the back will loop around the neck and under the shoulder and pull tight, making it almost as stable as a rifle.
Anyway, here's some pics:
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#23 AgentLQ

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Posted 13 September 2008 - 12:19 PM

So sick man.

Frigging awesome.
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#24 Azrial

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Posted 14 September 2008 - 02:06 AM

Interesting! I have thought of a 9mm Largo conversion for my Uzi or Mac-10.

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#25 sw8_2dg

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Posted 21 January 2013 - 11:03 PM

i'd like to know how you did this, what parts i need, etc. can you email me info?

tks






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