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Discussion Starter #1
Is there a 7.62X39 Improved cartridge? This is simlpy the parent with a 30 degree shoulder matching the angle for the 22 and 6MM PPC, but not pushing the shoulder back.

The 7.62X39 is one of my favorite cartridges to reload, because the industry specs call for a max of 50,000 CUP while factory loads are held to the 40-44,000 CUP range in deference to the AK and SKS actions out there. I load mine for a CZ Carbine bolt gun with 18 inch bbl and easily generate 2000 FPE with 130 gr Hornady PSPs @ 2650 fps. That's good for 2130 fps and 1300 FPE at 200 yards and a 4.9-inch drop sighted in at 100 yards.

2800 fps is within reach of this case, improved to hold 33 grs of water with a seated 125 or 130-gr bullet. Coupled with a 1 in 14-inch twist, this is a 0.25 MOA round. Most 7.62X39 rifles are 1 in 10 or less, which is way too fast for .308 to .311 bullets less than an inch in length. Might as well design it for a .308 bbl while we are at it. Think of it as a .308 Win with a 1-inch powder column length, designed to shoot bullets less than 1 inch in length.

I also use sabots and 55-gr .224 Hornady BTs in the 7.62X39, with remarkable results. Lil'gun easily drives these to 3500 fps and delivers 1.0 MOA. Pressure is moderate. Note that this is well over a .223 and close on the heels of a 22-250. The improved version will duplicate the 22-250. However, the suggested 1 in 14 twist would limit us to .224s lighter and shorter than the 55-gr spitzers. A 45 gr BT will do 4000 fps, guaranteed.

In the end you have a neat little rifle, 5 lbs in weight with 18 inch bbl and 2.3 inch bolt throw, covering varmints through deer, that is inexpensive and fun to shoot. You win the lightweight hunter class at your range every year and your bore and shoulder last forever.
 

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I have not seen a 7.62X39 Imp. I do know some folks were necking it up to 35 cal and reboring Mini-30's for it. Supposed to be a pretty good round. If no one has designed a 7.62X39 Imp. yet why don't you? If you applied Ackley's usual method it should work out fine. You'll just need to make a drawing and send it off to Clymer and have them make the reamer. Then send a few fired cases off to RCBS and they'll whip up some dies.

I was wondering how those little CZ carbines were. They sound pretty good but I don't think I have seen any cataloged lately. Maybe I'll have to look around for one.

Good Luck

Garth
 

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Hi, Gents:
IIRC, Mason Williams designed a .35x39 and wrote it up in Guns&Ammo. Basically .35 Remington performance in an SKS and with pointed bullets for better down-range ballistics. That's another one I'll look for in the pile up in the attic.

Of course you could straighten the Russian case out completely and get a .401 Winchester.

Merry Christmas & a Happy New Year
Jack
 

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Discussion Starter #5
I am thinking that the 35x39s must be improved, as there is not enough shoulder to headspace. I do shoot a number of .312 pistol bullets out of it and get 2750 fps with 100 gr HPs. Good devastating varmint round. The .314 lead balls @ 1400 fps are fun too.
 

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7.62x39

Paco, a writer in sixgunner.com did an interesting article on the 7.62x39, two actually (pt.1 & 2). It's called "30-30 on steroids".
 

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bull

loader said:
Is there a 7.62X39 Improved cartridge? This is simlpy the parent with a 30 degree shoulder matching the angle for the 22 and 6MM PPC, but not pushing the shoulder back.

The 7.62X39 is one of my favorite cartridges to reload, because the industry specs call for a max of 50,000 CUP while factory loads are held to the 40-44,000 CUP range in deference to the AK and SKS actions out there. I load mine for a CZ Carbine bolt gun with 18 inch bbl and easily generate 2000 FPE with 130 gr Hornady PSPs @ 2650 fps. That's good for 2130 fps and 1300 FPE at 200 yards and a 4.9-inch drop sighted in at 100 yards.

2800 fps is within reach of this case, improved to hold 33 grs of water with a seated 125 or 130-gr bullet. Coupled with a 1 in 14-inch twist, this is a 0.25 MOA round. Most 7.62X39 rifles are 1 in 10 or less, which is way too fast for .308 to .311 bullets less than an inch in length. Might as well design it for a .308 bbl while we are at it. Think of it as a .308 Win with a 1-inch powder column length, designed to shoot bullets less than 1 inch in length.

I also use sabots and 55-gr .224 Hornady BTs in the 7.62X39, with remarkable results. Lil'gun easily drives these to 3500 fps and delivers 1.0 MOA. Pressure is moderate. Note that this is well over a .223 and close on the heels of a 22-250. The improved version will duplicate the 22-250. However, the suggested 1 in 14 twist would limit us to .224s lighter and shorter than the 55-gr spitzers. A 45 gr BT will do 4000 fps, guaranteed.

In the end you have a neat little rifle, 5 lbs in weight with 18 inch bbl and 2.3 inch bolt throw, covering varmints through deer, that is inexpensive and fun to shoot. You win the lightweight hunter class at your range every year and your bore and shoulder last forever.
4000fps from a 7.62X39 Improved case using a 45gr. bullet and a sabot is very hard to believe. The pressure must be very very high. I've been shooting a Swift most of my life (I'm 63) and I know what takes to get those kinds of speeds. 18 in. of barrel and case full of powder isn't going to do it, unless you're way over pressured
 

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Hi, Gents:
Back when Remington was making the Accelerators, the 30-30 was rated at 3400 fps, the .308 at 3770 and the .30-06 at 4080, all with 55 grain bullets. The .30-30 load would have been held back by pressure constraints, but the .308 has a higher pressure rating than the .30-06. So there's no reason Remington couldn't have run the .308 load faster unless they were up against the pressure wall.

Bye
Jack
 

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A local gun store has (had?) a CZ carbine in 7.62X39 on the rack, a cute little carbine. But I have a 30-30, so didn't even play with it (much.)
Andy
 

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bodog said:
4000fps from a 7.62X39 Improved case using a 45gr. bullet and a sabot is very hard to believe. The pressure must be very very high. I've been shooting a Swift most of my life (I'm 63) and I know what takes to get those kinds of speeds. 18 in. of barrel and case full of powder isn't going to do it, unless you're way over pressured

I don't think "loader" was saying he had actually ACCOMPLISHED 4000 fps with a sabot'd .22 in a 7.62x39, rather that it was his OPINION that it was possible. I've done a great deal with sabot'd .22s and I think 4000 fps is "optimistic" from the 39mm case. However, I have developed duplex loads for most of the sabot'd small-cased cartridges (like .30 M1 - 3700+ MV) and it is most likely possible for the 39mm case too. And without exceeding 50,000 psi-ish.

Paul
 

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gitano said:
I don't think "loader" was saying he had actually ACCOMPLISHED 4000 fps with a sabot'd .22 in a 7.62x39, rather that it was his OPINION that it was possible. I've done a great deal with sabot'd .22s and I think 4000 fps is "optimistic" from the 39mm case. However, I have developed duplex loads for most of the sabot'd small-cased cartridges (like .30 M1 - 3700+ MV) and it is most likely possible for the 39mm case too. And without exceeding 50,000 psi-ish.

Paul
Sorry Paul, I just don't believe it. 3700+MV from a sabot load in a .30 carbine. ****, a 221 Fireball won't do that. If it is possible, why are we using the 220, 22-250, and 223 size cases to get more speed over the Hornet, bee, and all the other small cased .22? Slower powder, longer barrels is the key to controling pressure, and getting more speed.

I've got some sabots, and I tried them in a .32 Mag. 1700-1800 was about all I could get from my six inch Ruger.
 

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No need for apologies. I don't load for other people - I do it for myself. I'm really not 'into' high velocities - I kinda grew out of that phase. Regardless, duplex loads in my .30 M1 with 40 gr sabot'd .22s were smokin' along. The data is not diminished by your doubt.

WRT your rhetorical question "why are we using the 220, 22-250, and 223 size cases to get more speed over the Hornet, bee, and all the other small cased .22?" It's not that simple.

First because nobody really (myself included) wants to make duplex or triplex loads. It's far easier to get increased velocity with a larger case than it is to make multiple-powder loads.

Secondly, the bearing surface of various .22 caliber bullets relative to the cross-sectional area of the base of the bullet (bore diameter) is large as compared to the bearing surface of a .308 cal sabot to its bore diameter.

Third, the coefficient of friction of bullet guilding is an order of magnitude higher that that of the plastic sabot.

Next, accuracy, in my experience, with sabot's M1 rounds was abysmal. Six inch groups at 50 yds, and everything but the lightest projectiles key-holed at 15 feet.

Finally, the M1 action in semi-auto configuration is not equipped to handle the pressures associated with these velocites. My first attempt at sabot'd M1 rounds resulted in a broken bolt. Subsequent endeavors would require the gas port to be eliminated and the action operated in 'straight-pull repeater' mode.

Therfore, I think the reason we don't use duplex-charged, sabot'd .30 Carbine cases has little to do with muzzle velocity potential, and more to do with convenience and precision.

Paul
 

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Discussion Starter #13
Remington's Accelerators operated at 38,000 CUP, far below max. The problem is that there is no off the shelf powder that can burn progressively with such a light projectile in a big bore. Pressure drops like a stone as the light mass accelerates in the big bore.

If there were, you would get the same energy out of the light bullet as a heavy one. The 7.62X39 loaded to 50,000 CUP with R7 and a 123 PSP will do 2600 fPS for 1845 FPE. This energy with a 50 grain bullet is 4074 fps, its just that no off the shelf powder will do it.

Since we can't make powder at home, we need to make sabots and use heavier bullets. I have mine made by a local injection molding firm, and had great success with bullets 80 to 85% of the diameter of the bore with bore sectional densities not less than .150. The increased weight slows acceleration a lot, and allows the use of off the shelf powders.

If you stay within this envelope and use good materials for the sabot, you can get muzzle energies that equal to the parent cartridge. For example, an '06 will generate 2750 FPE with a 180 gr bullet, and will also do the same thing with a 100 gr 6MM bullet in a .308 Sabot. This is 3518 fps at 48,000 CUP.

I now have graduated to the 375 RUM which launches 180 gr .308 Noslers at 3675 fps at 60,000 psi.



Duplex might do it, or possibly a specially designed powder. Longshot is too fast, but it has the right characteristics.
 

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I just came across this thread, after having been away for a while.

About the 7.62x39 imp concept, I've got a friend/gunsmith not far from me, that talked me out of my stainless Ruger M77MKII in 7.62x39 (mistake ever getting rid of that gun), but he improved the chamber, by using a .310" pilot on a 240Wby reamer, and running it in just so that it cleaned up the shoulder/neck, retaining the same overall head/body diameter, but eliminating the body taper(I don't know the final dimensions), then uses Hornady neck-only sizing dies on his brass.

This "improvement" yields ballistics comparable to a factory loaded .300 Savage, albeit he's probably pushing the pressure envelope pretty hard. However, it's lights out for coyotes out to 300 yards with a dead-on-hold when sighted only 2" high at 100 yds using 123g SP's.

My friend doesn't own a chronograph, and I've only shot the gun up at his ranch.... don't know velocities, but he's positively eliminated case stretch... even with his steamy loads. Too, the case looks really cool with it's straight taper, and double-radiused neck/shoulder ala Weatherby.

It makes an interesting variation, and he already had the reamer, so it was a no brainer for a tinkerer like him to throw it into the lathe and "improve" it. I wouldn't do it, but fun just the same.

God Bless,
 

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Discussion Starter #15
Marshall -

Now that's a clever use of a 240 reamer!! I wonder if we could do that with a 6MM PPC reamer? Thanks for the tip.
 

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That's very interesting Marshall. Especially in a gas-operated rifle. I'd be inclined to try it, or some similar variation, in a bolt gun or a single-shot.

Paul
 

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Loader,

I don't see why not, the only reason my friend went with the Wby profile, was that he already owned the reamer! If you've got a reamer for the PPC series cartridges, it should be a snap to make an "Improved" 7.62x39, provided you can change pilots on the reamer. If not, I've seen pilots wrapped with teflon tape to bring them up to diameter for the specific task at hand with quite surprisingly fine outcomes..... food for thought.... we guncranks must have toooooooo much time on our hands!

God Bless,
 

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Oh, dear....the 7.62X39 Stanton has 31 grs of water case capacity and will drive a 135 gr bullet 2650 fps. This bullet has a SD of .203 and matches the trajectory of the new Remington .277 military round.

Wonder how much they spent on THAT one? I figure the average soldier will take the weapon that also shoots 7.62X39 given a choice. The improved round aslo solves the problem we have with feeding the 7.62X39 into the AR15 action.
 

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Come on Loader, they don't pay you enough to think that hard :)

Besides, it's much more beneficial to business associates and those you owe favors to reinvent the entire wheel.... not just put new bearings in the old one!

Makes one scratch their head at times!

God Bless,
 

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Discussion Starter #20
Oh Drat...now I really can't stop thinking...a 110 gr Hornady PSP adds 2 grs of case capacity and will do 3000 fps in the 7.62 Stanton. We gotta build one of these and have a friendly little match with thr REM.
 
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