7.62X39 AR Upper

[jhgtyre]

Brownells sells a 7.62x39 barrel for an AR-15 and along with a bolt and magazine that seems to be all you would need to convert to the bigger cartridge.  But, is it a good idea for 3 Gun use?  

Are magazines a problem?  I think they might be but if there is a source of decent high caps out there that would negate the mag issue.  

At first glance it looks like a conversion that would let you make major without as much recoil as a .308.  Then I begin to wonder why I haven't seen anyone use this setup....

Any information would be appreciated.

Thanks,

-jhgtyre

[BigDave]

Just looking at Winchesters published data on 7.62x39: 123gr @2355fps (@ muzzle) would only get you to ~289pf.  You need 340pf to make major.

With a 123 gr bullet, you would need at least 2764fps to make major.  I don't know if that is (1) possible or (2) if possible, safe with this cartridge.

[Mickster]

I have a Colt 16" 762x39 that makes a very handy little deer and hog gun here in the swamps of Florida. I've shot it in a couple of 3-guns also and really enjoy shooting it, even though it shoots minor with more recoil than a .223. I have some 20 and 30 round mags that work very well and I have some that don't work too well. Ya pays your money and takes your chances with these as they are all aftermarket and some of dubious quality.

I would be very interested in any research and experimentation data on the 762x39 that anyone has done for making major. I remember at one time that the 38 super was considered unsafe for major, but IPSC shooters are an inventive bunch and made it work. And you can always hope USPSA will lower the major/minor power factors a little bit for rifles, at least so the .223 will always make minor with factory ammo.

Anybody got any input on the idea of a major 762x39?

[jhgtyre]

BigDave,

Grrrr, I misrmembered what the major power factor was!  It looks like you would have to have a 150gr bullet going 2400fps to make major and I don't know if you can do that.  Wolf makes a 154gr round that should do about a 324 power factor but that is a long way from 360.  Thanks for the reality check though.

Mickster,

Are your mags marked or branded in any way that might help pick the good from the bad?  Do you know of a good source for them?

Even if it won't make major this still sounds like a fun gun.  

Thanks,

-jhgtyre

[BigDave]

Maybe Olympic?  I think they might have been the first to make a x39 upper/rifle.

[Mickster]

jhgtyre

Several years ago I picked up some of the USA mags at a gun show. They are an oddball mix of a steel AR upper spot welded to a steel AK lower. The 30 rounder doesn't function well with more than 25 rounds in it and even so isn't 100%.  A couple of the 20 rounders would spout out a couple of rounds at a time while shooting but work perfectly now that I tweaked the lips a bit. The other 20 rounders worked fine out of the wrapper. USA doesn't have any but they still turn up at shows.

Next are some steel 20 rounders that look identical to .223 30 rounders except for the follower, lip width and the body's are flat sided, not ribbed like a .223. I got some from Tapco and some from Cheaper Than Dirt and these work perfectly. You can get 23 rounds in these.

Currently, the only source I know of for 762x39 AR mags is Cabellas. I just called them and they have some in stock for $19.99 each. They have the 20 rounders which I believe are the same manufacturer as what Tapco and CTD have/had.

Do you think this idea of 762x39 major is out of the question? I don't know much about gunpowders but some of the new ones get good velocities at low pressures and that seems like the place to start. Anybody got any ideas?

[Carlos]

I did the numbers a few months back and 7.62x39 was just barely below major for published loads (then again, everyone  knows that 38 super can't safely be loaded to major according to published data!). The 7.62 mags used in the AR seem to be the issue; check out Glen Zediker's excellent AR book about PPC cals as to mag reliability. Even with the best mags, capacity seems limited to 26 (still better than the FAL's 20, but not as good as a .223 Sterling 40 rounder). 3 more thoughts:

The 300 Whisper loaded w/ .308 cal bullets in the 125 range comes close to the 7.62x39. Would it make major? Maybe. Works in any .223 mag w/ same capacity.

The old wildcat .223x6mm (necked up to 6mm) might come close to major - so would the PPCs but then you are back to mag problems and LTD capacity.

I think Kelly used a modified FAL in 308x6.5 (AKA 260 Rem) in the last nats - and did quite well! The AR-10 in that cal w/ a good comp might be just the ticket.

D.

Afterthought - make sure barreled upper has a .308 bore and not the larger .311 up to .314 barrel bore since bullet selection is limited w/ larger bore. I know Mini 30s had .308 barrels - I think Colt brand also used .308 and NOT the .311 bore found on AKs/ other factory 7.62 guns.

[jhgtyre]

Thanks for the mag info Mickster.  Having a place to start the hunt is good.

Carlos, forgive my ignorance, but wouldn't the mags hold the same number of 6mm rounds as .223's if the 6mm's were just necked up .223's?  Or does the mag need the curvature to fit a few extra in so a straighter case doesn't fit as well?

Thanks for all the info.

-jhgtyre

[Mickster]

Carlos

You are correct on the bore size of the COlt not being .311 or .314. When I first starting playing with mine years ago I did some measuring cause it shot 1moa (sand bagged, 6x scope) with some ammo. I slugged my Colt barrel several different times and got .3095 each time. Best of both worlds I guess cause it got the 1" moa with Norinco (.311) and US factory. I still get 3 shot 1moa with handloads using 130 grain Speers.

Anyway, it's a fun gun but .223 is more sensible if you have to shoot it minor. I like all this info on major rifle though. Shows that maybe there is hope.

[L9X25]

Mickster,

As if you haven't heard enough from me lately...

I agree with your belief that a 7.62x39 should be able to do much better than is currently published.  I know you are vividly aware of my 9x25 carbine, but you may not know that it currently sends a 115gr bullet 2000+fps with my normal IPSC pistol load, has no pressure signs, and has MUCH more powder capacity available in the case.   Because the carbine is a total blowback design, I have no intention of testing the limits of the caliber in this weapon.  I do feel that, with a more robust action, this caliber could easily match published 7.62x39 performance.  You cannot even compare the powder capacity of a 9x25 with a 7.62x39.

Leo

[Mickster]

Well Hi There Leo

I love that little carbine conversion you have. I was looking at one in .40 so I could use it with my Para lower and shoot in some of these pistol caliber carbine matches around here.

From what I've read on this thread it looks like it would take some serious R&D to get the 762x39 to make the USPSA major power factor, if at all in a semi-auto, and there are better choices out there for that end. I'll just stick with my .308 FAL to shoot major for now and my .223 for minor.

Hope to see you at the next 3-gun in Orlando.

[L9X25]

Mickster:

I'm thankful that I will be shooting the carbine this weekend... they claim that the match will be comprised of 7 stages featuring 75 shotgun shots and 125 rifle and 50 pistol.  I don't even want to carry a major rifle or shogun long enough to shoot 200 rounds!   It will certainly be an experience!

See you there,

Leo

[Tokarev]

Any further info on this? I think a 180-grain round nose bullet could be used to make major without too much trouble. It'd have to be seated deep but the shank on a round nosed bullet would be long enough to allow you to seat the bullet to the correct overall length. Feeding with a blunt bullet may be an issue in semi rifles.

I have a post-ban AK and a box of Hornady .312 174-grain round nose bullets. I'll try to make a few riounds with AA#2200 and see what happens.

[Patrick Sweeney]

Problems abound, but they can be solved if you're willing to be inventive and determined:

Making Major. The listed data puts 7.62X39 "just" under major. You can push it, but you are strictly on your own.

Magazines. If you use AR mags, the case taper is wrong, and capacity is less than with .223.

Barrels. The Colt 16" is not what I'd select for velocity or accuracy. Plenty good enough for blasting, but not for match use. Going to a match tube greatly increases cost.

Brass. Expensive, especially compared to surplus or Wal-Mart priced .223.

One solution would be to alter the case to some sort of 7.62X39 Improved. You'd alter the taper to better fit the AR mag curve. It would also get you more case capacity, allowing an easier workup to Major. Ideally, one way would be to work backwards from the 7.62X45 Czech case. (Good luck finding those in brass boxer style.) Shorten to allow full mag length, case taper to mag curve, max capacity, etc. Then load to Major.

If you're doing all that, why not just make it a 6.5 for better ballistic coefficient? At the ned of it all, you'd have as much in the gun as if you'd bought a new AR-10 or SR-25 and downloaded it to just be Major. But boy you'd have fun getting there.

[Mickster]

Tokarev

Be sure to let us know how that load works out. Even though there are many other paths to take to try and make major in an AR-15 as mentioned above by some very knowledgable people, I'm still hoping for the path of least resistance to materialize... a heavy bullet with enough powder for the x39 to make major.

Speaking of x39 AR-15's, at a match I overheard someone mention a company that makes an AR lower receiver that takes AK-47 mags. Does 30 or 40 rounds of major x39 sound interesting?

[Tokarev]

The place with the 7.62x39 AK/AR lower is Tactical Weapons in Mesa, AZ. I haven't seen an actual firearm, just his website and ad in "Shotgun News." This might be just the ticket if it's reliable and accurate.

My AK will be the project gun for the time being. I just want to load a few rounds with enough powder to cycle and go from there. I want to make sure the bullet stabilizes, etc. before I see about pushing it to major with the AK's 16" barrel.

If this works, it'll give me a reason to buy a Krebs KTR-03 that I've been lusting after!

Anyway, I spoke to Johann at Accurate Powders and he says 20 grains of 1680 or 21 grains of 2200 should be safe as a start load.

I'll post more when I have it.

[Tokarev]

Oops! I forgot to mention that the website is www.tactical-weapons.com or www.ar47.com

[Tokarev]

Here's a loaded round using the Hornady .312 diameter 174 grain RN bullet. I've got it loaded with 21 grains of AA 2200 powder. I haven't had a chance to get to the range and do any testing. I'll post more info here when I finally do.

http://www.printroom.com/ViewAlbum.asp?use...album_id=154024

[GvU]

In this years Nordic Rifle Championship the winner (Finland) in "semi-auto standard" used a 185 grain bullet (probably Lapua) in a Sako (AK-type/Valmet). I don't know loads etc.

So you need to go to heavy bullets (and reloading).

Their reason for using 7.62x39 is availability of brass, bullets. .223Rem was more expensive to them.

In open someone was shooting (open/comp, minor) lightweight 7.62x39 with (56 grain bullets with an aluminium core). His complain was that the heavy bold was moving his gun around more than his load.

John

[Patrick Sweeney]

I've seen at least one AR converted to take AK mags, and ugly hardly begins to describe it. One problem we might have to deal with in using heavy bullets to make Major in a 7.62X39 case is trajectory. According to the Nosler charts, a 170 or 180 .308" @ 2000 fps drops 18" to 36" (depending on drag) at 300 yards. Bullet selection, and trajectory knowledge, will be critical.

[TBF]

If anyone is interested, I have been playing with 85 gr. bullets ( .312 ) in this caliber, not nearly finished, but might make an interesting MINOR load.

Surprisingly AK's will feed really short rounds.

Travis F.

[Tokarev]

I made it to the range with ten rounds of "heavy ball" loaded with the Hornady .312 174 grain round nose and 21 grains of AA2200 as discussed above. The good news is that the bullets stabilize and accuracy is on par with standard ammo in my AK. Groups run about 3-4" at 100 yards with the stardard AK sights. The rounds hit at about point of aim for elevation but I had the drift the front sight to the left for windage.

Anyway, the bad news is that the battery is dead in my chrongraph. I'll make another trip out with a fresh battery soon.

Case ejection is standard Ak with the brass flying about 15 feet away. The primers look fine and I see no evidence of stretched cases, etc.

[Tokarev]

I found a guy on the AK board that says he's been using a Sierra 180 SPT for use in his subsonic loads and has had no trouble seating them to the correct OAL. He also says they feed fine in his rifle. I will have to get a box and give them a try. I went with the Hornady round nose bullet because I had them on hand and because I thought a spire point would be too long to seat correctly. This new information changes things and I'll post here when I have some more news.

Also, I think CORBON makes (or made?) a 150 grain hunting load with an advestised velocity of 2350 fps or something like that. Have any of you guys seen any of this? I looked on their website but didn't see this load listed.

[Tokarev]

Well, I shot 5 rounds over my chronograph at a distance of ten feet from the muzzle. I'm going to need more gunpowder! The average velocity was 1507 fps with a standard deviation of 38 fps. That means I'm about 375 fps under making IPSC major. I'll try loading up to 25 grains with AA#2200 and see where that gets me. Johann at Accurate told me somewhere around 25 grains would be max.

From looking at various loading data on the 7.62x39, I think VV-130 may be the powder to use. Too bad I can't find any on the shleves as I hate to order a small quantity. HAZMAT is a killer!

[chp5]

It would be very interesting if (like with pistols), USPSA/IPSC lowered the major PF. If the major PF was something around 275 or so, shooters could make major with the 7.62x39, but not with the 5.56. I think you’d see a lot more shooters using AKs.

It could also be an avenue to let newer shooters (or shooters with less disposable income) use a $300 rifle and cheap ammo and be more competitive because they can make major. Similar to Production division in pistols, I think it could potentially draw more entry-level shooters to 3 gun matches – which, IMO, is a positive thing.

yes . . thread drift . . .