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MMcfpd
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Posted: 4/11/2008 3:12:39 PM
Questions keep coming up about putting together AR-15s chambered for 7.62x39mm, so here's what I know as of April 2008.

Manfacturers who currently offer 7.62x39mm upper receivers include Del-Ton, DoubleStar, DPMS, Model 1 Sales, Olympic Arms and Sabre Defense for uppers that will go right on a standard 5.56/.223 lower; Colt also produced a 7.62x39mm Sporter model that is out of production but findable on the used market and Armalite is said to have one available in the very near future. MGI has a modular magazine lower receiver system that allows use of an AK magazine and the AR47 is an out of production lower that also allows use of AK magazines.

A quick look at the standard configuration production uppers shows them all being offered as 16" carbines and 20" rifles. Commentary I've seen here has been to the effect that there's not much appreciable difference. All seem to be produced with 1:10 rifling and none are chrome lined. Model 1 Sales also offers an 11.5" 7.62x39mm pistol upper.

Be aware that the Model 1 barrels have a 1/2 x 36 thread pitch, so muzzle device options are limited. All I've found besides the A2 FH that is standard is a Phantom FH.

MGI produces bolt carriers modified to clear AK mag feed lips. MGI also has a bolt and firing pin combo optimized for eastern European steel case ammo.


Originally Posted By twl:
It has a normal 7.62x39 AR15 bolt which has been reamed in the firing pin channel for a re-profiled and extended firing pin.
This firing pin has a new profile which will strike deeper and more fully than a normal AR15 firing pin, and will be much more reliable in striking for the Wolf and Combloc 7.62x39 ammo.

The pin provides the correct tip protrusion thru the bolt face, and is large enough diameter on the tip to prevent primer piercing, while still striking deeply enough and fully enough.


It's been advised in the past that one part subject to breakage is the bolt, so I have a spare, but with ~1600 rounds through a Model 1 upper, I've had no problems yet. A carbine buffer and spring have been working well also.

While I personally think this conversion makes a great platform for the 7.62 round that smokes the Kalishnikovs and SKSs both in accuracy and ergonomically, the weak point at this time is magazines.

Magazines I have tried:

• 7 rounds in a standard 5.56 magazine works OK.
• Colt made 5 rounders that work; these magazines are out of production.
• USA made some 10 rounders that have worked for me, with some FTFs - they work best loaded with just 8 rounds - while others have reported no luck; these magazines are out of production.
• MWG makes plastic 5 and 10 round mags that did not work at all for me, while others have had better luck.
• USA also made the so-called "Frankenmags" which were an AK mag body grafted to an AR mag "head," and, while they're also out of production, the 20 and 30 rounders do seem to work. I've got one such 40 rounder and it's a bit unwieldy.
• National Magazines has recently put out an 18-20 round magazine for this application - I bought and tried one and it did not work at all satisfactorily (dropped out of the gun after every shot).
• C Products has new production 5 and 10 rounders and the 10 rounders I've used perform well.

On the horizon are C Products very-soon-to-be-released (we hope) 30 rounders, to be followed by new 20 rounders.

Of course, with MGI's modular system or an AR47, you can use AK magazines.

That's all I can think of right now. Corrections and additions are welcome.
308Sako
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Posted: 4/11/2008 3:18:17 PM


1 in 12" twist
MMcfpd
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Posted: 4/11/2008 6:07:23 PM
Is that Colt chrome lined?
nugentgl
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Posted: 4/11/2008 9:28:03 PM
[Last Edit: 4/12/2008 8:55:23 PM by nugentgl]

Originally Posted By MMcfpd:
Is that Colt chrome lined?


NO. As of right now, there are not 7.62x39 bbl's that are CL.
Xerxes - I have so many archers that their arrows will blot out the sun.

Spartan - So much the better, we shall fight in the shade.
ArticWolf
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Posted: 4/13/2008 1:04:41 PM
[Last Edit: 4/13/2008 8:24:04 PM by ArticWolf]
My Colt Sporter AR-7.62x39 is a 1/12 twist. I have found that several after market Mags have failed to be reliable to the point that I would NOT go into combat with them. However, the 1st generation of the C Products 25rd AR-7.62x39 Mags worked GREAT for me while others had some issues. Larry and his staff are waiting on the last item (followers) to be able to ship their 30rd AR-7.62x39 Mags.

When I obtained my Colt AR-7.62x39, the original owner had cycled 500rds of Wolf FMJ ammo. I first treated the Colt with Microlon and have since added anther 2,500 rounds (without any oils/lubes) of Wolf, Winchester, and reload ammo with FMJ/HP/SP bullets with just a few FTF.

I am looking forward to producing another video for C Products of the performance of their 2nd generation of 30rd AR-7.62x39 Mag. At present you can see the performance of their 10rd AR-7.62x39 Mag from their home page.

After the treatment of Microlon, I was able to pull my 100yrd groups into ½”, where before the treatment, we had 1” groupings. I can’t say enough about this product! Cleaning is a snap, and being from the Deserts of Arizona, I have NO problems with dust or sand buildup within this AR-15 that others have to deal with.

Your fun will begin when you start to get into reloading for this round and experience the improved performance of the 7.62x39 used in an AR-15! My son said that for plunking the 5.56 are fun, but “I GOT TO GET ME ONE OF THESE”!

ArticWolf



Boomer
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Posted: 4/14/2008 4:14:01 AM
Colt manufactured it's 7.62x39 Sporter Light, Model R6830, from 1993 until I believe abouit 1998. This was a carbine length AR with A2 buttstock, A2 upper receiver, 16" barrel, etc. In addition, they also offered flat top upper receiver assembly conversion kits with both 16", Model R6850DC, and 20", Model R6851DC, barrel lengths.

I picked up a couple of R6830s back in the day during the AW ban because they were under-appreciated at the time and I got great deals on them despite being pre-ban ARs. The first was purchased as a factory original R6830. The second as a lower receiver assembly and I subsequently sourced a Colt R6850DC 16" upper receiver assembly conversion kit and added M4 handguards and an M4 stock for a sweet little carbine.



Original Colt ad for the R6830 from the 1993 New Products brochure:



Magazine have always been the Achille's heel of the 7.62x39 AR-15.

Pretty much any USGI 5.56 magazine will work reliability with 5-6 rounds of 7.62x39. After that, the cartridges begin to bind up and jam.

Colt first used regular USGI 20 round magazines with internal blocks to limit capacity to 5 rounds of 7.62x39. These internal blocks were easily removed after which the magazine would function just like any other USGI 20 round magazine. After the ban they switched to a cut down USGI style magazine feed tower with a unique composite base to prevent them from being converted back into 20 round magazines in violation of the AW ban at the time.

Because the 7.62x39 AR15 appeared relatively shortly before the AW ban and never really gained much popularity in that time, development of high capacity magazines for it was limited. While there were some stamped sheet metal magazines from companies such as Triple-K, Western, USA, etc, the only ones worth a darn were what are essentially hybrid magazines; AR15 style feed towers welded or riveted to AK47 style bodies. Scherer and Gordon Technologies magazines are the most robust of the preban high capacity magazines. These are aftermarket steel AR towers TIG welded to genuine AK47 magazine bodies with similarly genuine AK47 springs and followers. Surprisingly, despite otherwise having a reputation for total crap, USA had some good high cap 7.62.39 AR magazines that used their own AR style steel feed tower spot welded to their proprietery AK style body, spring and follower and they work very well.

Here is a pic of the various types of 7.62x39 AR15 magazines I have collected over the years:



Top row, left to right: MWG 10 round, Colt post-ban 5 round, Colt pre-ban 5 round.
Bottom row, left to right: Scherer 30 round, G-Tech 30 round, USA 20 round, USA 30 round.

The Scherer and G-Tech mags are nearly as robust as an AK47 magazines. One could probably drive nails with them if necessary.

I am now anxiously awaiting C-Products release of their 30 round 7.62x39 AR magazines for evaluation.
Hyperbaric
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Posted: 4/15/2008 1:11:25 AM
[Last Edit: 4/15/2008 11:39:49 PM by Hyperbaric]
Will muzzle brakes from .308 AR's work properly on a X39?
Benjamin - Mystic, CT
mutwagn
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Posted: 4/15/2008 2:24:10 PM
MGI also has a bolt and firing pin combo optimized for eastern European steel case ammo.


Originally Posted By twl:
It has a normal 7.62x39 AR15 bolt which has been reamed in the firing pin channel for a re-profiled and extended firing pin.
This firing pin has a new profile which will strike deeper and more fully than a normal AR15 firing pin, and will be much more reliable in striking for the Wolf and Combloc 7.62x39 ammo.

The pin provides the correct tip protrusion thru the bolt face, and is large enough diameter on the tip to prevent primer piercing, while still striking deeply enough and fully enough.


It's been advised in the past that one part subject to breakage is the bolt, so I have a spare, but with ~1600 rounds through a Model 1 upper, I've had no problems yet. A carbine buffer and spring have been working well also.

While I personally think this conversion makes a great platform for the 7.62 round that smokes the Kalishnikovs and SKSs both in accuracy and ergonomically, the weak point at this time is magazines.



I have been interested in this conversion for awhile.
With no cheap 223 ammo available any more, and with C-products coming out with reliable mags, it looks better all the time.
Will the MGI bolt and firing pin work with the standard AR15 bolt carriers? It seems there bolt carrier is mainly intended for use with there lowers that are made for the AK magazines, and is not needed if you are using a standard AR lower.
Has anyone had any experience with the Del-Ton barrel and bolt assembly? If so was there any trouble that wasn't due to a magazine problem.
twl
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Posted: 4/15/2008 10:47:57 PM
The MGI bolt/pin kit for 7.62x39 will work in a normal AR15 or M16 bolt carrier.
MGI Sales Representative for AR15.com, and the internet
Call 423-746-9019
or email twlyons@juno.com
CALL ME TO ORDER YOUR MGI PRODUCTS !!!!!!!!!!!!!!!!!!!!!
bnr32gtr
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Posted: 4/16/2008 3:32:14 AM
Great info! Who makes M4 profile barrels in 7.62x39? I remember seeing several places a couple months ago but can not seem to remember them or find them in my bookmarked favorites. Would like my 7.62 upper to look like my .22 and .223 uppers.

Thanks and let's keep supporting Larry and the gang over at C-Products in the hopes they will come out with 20 and 30 rounders again! Mike D.
MMcfpd
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Posted: 4/16/2008 8:57:16 AM

Originally Posted By bnr32gtr:
Great info! Who makes M4 profile barrels in 7.62x39?


Sabre Defense lists M4 profile 7.62x39mm AR barrels - 16", 1:10, not chrome lined, kinda pricey.
Meat-Head
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Posted: 4/16/2008 11:09:54 AM
I would love to have one of the MGI bolt and firing pin sets but man are they pricey!!! $125 for just a bolt and pin is more than I want to spend. If the price comes down I will definitely buy one.
RedFalconBill
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Posted: 4/16/2008 12:24:09 PM

Originally Posted By MMcfpd:

Originally Posted By bnr32gtr:
Great info! Who makes M4 profile barrels in 7.62x39?


Sabre Defense lists M4 profile 7.62x39mm AR barrels - 16", 1:10, not chrome lined, kinda pricey.


Sabre offers chrome plating as an upgrade in 5.56 and 6.5 Grendel.

Call and ask them if they offer this option for the 7.62x39 as well.
MMcfpd
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Posted: 4/16/2008 7:40:24 PM
Some compensator info

From an older thread: 7.62x39 Compensator


Originally Posted By trg42:
The thread is the same as a "Colt Style" 9mm pistol barrel. I tried both the RRA A1 style style in 1/2-36 and the Smith Enterprise Vortex for the 9mm.

You can buy both from RRA. The A1 style is only $11 so you cant go wrong

rockriverarms.com/index.cfm?fuseaction=category.display&category_id=243 (made it hot - MMcfpd)

or the Vortex from Brownells

www.brownells.com/aspx/NS/store/productdetail.aspx?p=25230&st=vortex%209mm&s= (made it hot - MMcfpd)

The 9mm bullet is .355 so the clearance is slightly big for the .311 of the 7.62X39 but thats ok . I run have a Sako brake made for the 338 that I run on a 308 as well that still makes a significant difference ( even though the clearance is too big )


And:


Originally Posted By MikeinGA:


Originally Posted By Wolfman223:

Originally Posted By MikeinGA:
I got a muzzle brake from EGW(Evolution Gun Works in Quakertown,Pa) They made me one, but when I received it I checked it out and the bore in the brake was the same as the bullet size(.311). I had to bore it out the correct size. I am glade I did it or would had a bullet stuck and maybe wasted my gun or others around me. It cost me $95.00 plus setting up and renting time on a lathe to bore it out. It cost in the end $115.00. I will not buy from them again, gun parts need good QC or someone could get hurt or killed. IMHO.

Mike



Mike: What was the correct size you arrived at to bore that out from the .311 size to use the brake?


I made the bore 30 thousands of an inch over to make it .341 and broke the sharp edge of the front of the bore in each chamber to make it like a muzzle of a barrel. I will not get to test it till next week. I put the same type of brake on my .223 AR, now I have shot both uppers with flash hiders and with flash hiders to get a base line group of 5. I will give a range report after testing.

Mike
RedFalconBill
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Posted: 4/17/2008 12:32:48 AM
Oh, PWS is going to offer 7.62x39 uppers with their gas piston system....sometime.

Here: Official PWS Piston System Release

Were it me, I would eschew the 1/2"-36 thread with a 7.62x39 barrel from Model 1 Sales. IMO not enough material left over after threading.

Better to order the unthreaded barrel, then have it threaded for the AK-47 14x1 LH.

YMMV.
bnr32gtr
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Posted: 4/17/2008 3:52:12 AM

Originally Posted By MMcfpd:

Originally Posted By bnr32gtr:
Great info! Who makes M4 profile barrels in 7.62x39?


Sabre Defense lists M4 profile 7.62x39mm AR barrels - 16", 1:10, not chrome lined, kinda pricey.



Thanks for the info. Kinda pricey!? Damn! Maybe I should just buy a regular 16" barrel and have my machine shop spin it up on the lathe.... Mike D.
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Posted: 4/17/2008 8:21:12 AM

Originally Posted By RedFalconBill:
Were it me, I would eschew the 1/2"-36 thread with a 7.62x39 barrel from Model 1 Sales. IMO not enough material left over after threading.

Better to order the unthreaded barrel, then have it threaded for the AK-47 14x1 LH.

YMMV.


I've got one of my 7.62x39 barrels threaded 5/8"-24. Same thread as the M60 as well as what some AR10 barrels use.
I'd recommend that over the AK thread as there are more accessories available including sound suppressors.
RedFalconBill
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Posted: 4/17/2008 10:06:21 AM

Originally Posted By amphibian:

I've got one of my 7.62x39 barrels threaded 5/8"-24. Same thread as the M60 as well as what some AR10 barrels use.
I'd recommend that over the AK thread as there are more accessories available including sound suppressors.


For suppressors, your suggestion is the better one, by far. Thanks for mentioning it because there might be those who are interested in both (suppressors and the 7.62x39 upper).

For Flash Hiders and Compensators, there are more then enough regardless of which way you go.

steezo757
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Posted: 4/18/2008 3:36:26 PM

Originally Posted By RedFalconBill:

Originally Posted By amphibian:

I've got one of my 7.62x39 barrels threaded 5/8"-24. Same thread as the M60 as well as what some AR10 barrels use.
I'd recommend that over the AK thread as there are more accessories available including sound suppressors.


For suppressors, your suggestion is the better one, by far. Thanks for mentioning it because there might be those who are interested in both (suppressors and the 7.62x39 upper).

For Flash Hiders and Compensators, there are more then enough regardless of which way you go.



Here's my 7.62x39 setup.

My barrel is threaded in 1/2-36. Tim at SAS made a mount for my .30 cal can with 1/2-36 threads.

MMcfpd
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Posted: 4/19/2008 11:17:17 AM
Another little bit from Life expectancy for 7.62x39 bolts:


Originally Posted By twl:
The 6.8SPC bolt "should" be stronger than the 7.62x39 bolt, "all thing being equal", because there's about .010" more supporting thickness under the lugs in the 6.8SPC bolt. And the 5.56 bolt "should" be stronger than either of those two, for similar reasons of supporting material under the lugs.

...

However, if you are actually using 7.62x39 ammo, and not using the bolt in a "wildcat" caliber or hot reloads, the pressures seen from the 7.62x39 ammo are low enough to pretty much compensate for the reduction in lug support, and should not pose a major problem to the longevity of the bolt. As long as it is a quality bolt.



Originally Posted By twl:

Originally Posted By JFA:
Far as I understand the buffer and spring don't come into effect till after the "explosion" and the bullet is gone.


Some types of buffers can delay the extraction timing, which is a big issue for reliability in carbines, and can affect bolt life(primarily at the cam pin hole breakage point).

Heavy buffers will also do this.


And some older 7.62 pics I had.

7.62x39 AR chamber and ramps:


5.56 (left) and 7.62x39 (right) bolt faces:


7.62x39 bolt catch dings - never did figure why the bolt was hitting it, although the problem's gone away:



7.62x39mm USA 10 round mag:


7.62x39mm MWG 5 & 10 round mags:


7.62x39mm Colt 5 round mag:


National mag (new production) that doesn't work:



Other mags I've tried:


And my Model 1 7.62x39 AR almost in its current state (Geissele FCG added since the photo):

warchildindy
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Posted: 4/20/2008 1:50:56 PM
[Last Edit: 4/20/2008 2:31:33 PM by warchildindy]
The Osprey piston conversion kit is interesting. When the kit is offered to civilians, I wonder, if the kit would work with the 7.62x39?

The Osprey kit will work with about any style of hand guards and is cheaper in price. The more possible options, the better.

I have a 7.62x39 DPMS 16" carbine upper, on a Stag lower. I have ordered and will try a Wolff extra power spring with a H3 buffer to slow the bolt down, and hope to control any bounce. I will probably pick up a MGI 7.62x39 bolt, as a back-up to the DPMS bolt, for the moment.

I have heard of someone using the 25 round 6.5 Grendel mags with the 7.62x39, without any issues. If that is true, that is possibly, another option for a higher capacity mag.

The 7.62x51mm was the original AR platform caliber and it works today. I see the 7.62x39mm usage in a similar platform as a good experiment; with great end results. It will take time to resolve these operational issues.

I am biased, I like the old M43 round. Thanks for great information, as always.
RedFalconBill
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Posted: 4/21/2008 9:21:04 AM
It looks like CProducts will soon be shipping.....


Originally Posted By CProducts:
Sort of reminds me of that Old TV commercial... " Anyday now, anyday..."

In this case it will be true!


The new followers will be at C Products on Tuesday the 22nd and we will be at the range to test them. We should be able to start assembling magaines late next week. Finally!!

Larry


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Posted :: Yesterday 12:11:34 PM EDT
ArticWolf
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Posted: 4/21/2008 12:19:39 PM
MMcfpd,

Looking at your photo "7.62x39 AR chamber and ramps:" I have never experienced what you have shown here. I would be looking for answers from the manufacture on this one.

ArticWolf

MMcfpd
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Posted: 4/22/2008 7:18:08 AM
I'm not sure I understand, Arctic Wolf.
Qball
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Posted: 4/28/2008 12:48:31 AM
Anybody running a 7.62X39 upper on a Cav Arms lower? if so are you running a heavier buffer and spring?
MMcfpd
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Posted: 4/28/2008 7:42:25 PM
I might just try that whenever my Cav Aid lower appears.
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