The 7.62x39 bench gun is no more, I give you .30PPC Largo


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R.W.Dale
March 1, 2009, 07:18 PM
Since building the now famous 7.62x39mm bolt gun I feel I've managed to prove my point about this cartridges accuracy potential. Leaving me to pursue bigger and better things.

I was looking for a chambering that would give me more velocity ( read case capacity) to reduce my time in flight on 300m targets without resorting to overkill with the ever present and frankly quite boring 308win. Oddly enough there are NO cartridges in between 30-30 which was too small to clean up my chamber and 300sav which is really no different than 308. So what I ended up doing was something I never thought I'd do. I resorted to wildcatting.

Here's what I did. I took a 6mmPPC reamer and fitted a .300 pilot and then ran it into the x39 chamber far enough to clean up the original shoulder and remove just about all the case taper. Then being a Savage (thank you) I simply ran the barrel in against a 7.62x39 GO gauge and set the BBL nut for a slight short chamber that facilitates that crush fit of the neck shoulder junction needed for "improved" rounds to fireform factory ammo. In this case the shoulder ended up being farther forward than the other PPC's hence the "Largo" denomination.

While not a huge increase I gained appx 5% more case capacity that's good for 2.5 more grs of H335. But I'm hoping the biggest improvement will come from a much more stable brass shape and a more pronounced shoulder.

Left RP 7.62x39mm, Right fireformed .30PPC Largo
http://i3.photobucket.com/albums/y96/krochus/Stevens%20200/HPIM2367.jpg


Surprisingly I lost no accuracy when firing conventional x39 factory and handloads. I fireformed over 40 rds today and had NO misfires with 20 factory rds and only one with handloads using rather short to the shoulder virgin remington brass that fired on the second strike. The best thing is that my Lee 7.62x39mm collet die will still work with this new round.

So waddya think?

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gripper
March 1, 2009, 07:42 PM
I like it!

gvnwst
March 1, 2009, 07:43 PM
SWEET! I have been thinking of a .30 version of the 6.5 grendel, you just did the actual work for me!:D

Brian Williams
March 1, 2009, 08:00 PM
That looks sweet, a bit of a short neck, any problem with bullet setback or being loose.

db_tanker
March 1, 2009, 08:33 PM
with the short neck it does look alot like a short body 300 Savage...but I think that for 150 flat base bullets and smaller it would be a sweet number.

R.W.Dale
March 1, 2009, 09:58 PM
about the neck

The pics are somewhat deceiving because on the new cartridge the neck shoulder junction is much more pronounced than the parent case, BUT It's not really any shorter than it is on 7.62x39 which seems to work fine, bullet setback isn't a concern as I'm shooting these in a single shot bolt gun

with the short neck it does look alot like a short body 300 Savage...but I think that for 150 flat base bullets and smaller it would be a sweet number.

With a 1/15" twist barrel that's what I'm limited to


I'll load up some ammunition later and post pics of the finished cartridges

SSN Vet
March 1, 2009, 10:29 PM
This has surely been an interesting project rifle of yours Krochus.

Now, your taking it into new teritory.

Thanks for posting it.

stubbicatt
March 1, 2009, 11:50 PM
7.62x39 Ackley Improved. LOL.

Deer Hunter
March 1, 2009, 11:56 PM
I love this.

:D

Funderb
March 1, 2009, 11:58 PM
so, its effectively a nontapered 7.62x39 round? this is cool

JWF III
March 2, 2009, 09:30 AM
7.62x39 Ackley Improved.

Correction-7.62x39 Krochus Improved

Wyman

NCsmitty
March 2, 2009, 01:21 PM
Nice job krochus, very efficient looking chambering and wise use of original loading equipment.

NCsmitty

TMM
March 2, 2009, 02:02 PM
Interesting! have you tested the accuracy yet?

tmm

alemonkey
March 2, 2009, 08:02 PM
Ok, at first I was bummed thinking you got rid of the 7.62x39 gun, because it's such a cool rifle. But now I'm really excited to see how this turns out.

telomerase
March 2, 2009, 09:37 PM
Another post by the alien invaders who seek to conquer us by creating so much ammo incompatibility that we are functionally disarmed :scrutiny:


:neener:

gvnwst
March 6, 2009, 02:27 PM
I know it has only been 4 days, but you gotten to the range and tested accuracy yet? I await the results:D

jerkface11
March 6, 2009, 02:30 PM
Do you really think he would wait more than 4 days to go to the range? Heck he only lives a mile from it.

gvnwst
March 6, 2009, 02:37 PM
Um, i didn't know that?:confused: Although, i live only 20 feet from mine:neener::neener::p:D

R.W.Dale
March 6, 2009, 04:52 PM
Sorry for the delay but 12hr work days keeps me quite busy.

I've had it to the range and shot a couple different loads thus far. But at this point I really don't have anything to report. It shoots just as well as it did before but at this point I'm still trying to figure out how to load for this cartridge propellant wise. It seems as though this new case shape will allow me to step up pretty much one range of powders slower and keep the same velocity as before but at lower pressures.

An example is now with 150grn bullets can use Varget to get the same speeds as H335 yielded before, I'm hoping at the other end of bullet weights 100/110grn I can get away from what are pretty much slow handgun powders (aa1680 & N-120) and step up to a RE7 or benchmark and still get 2800fps +/- but with lower pressure and thus longer case life.

When I iron out some of these issues I'll post a much more comprehensive range report, It'll just take a few trips to the range.

jpwilly
March 6, 2009, 05:18 PM
Varget will fill the case too much try BL-C(2) it's slightly slower too http://www.hodgdon.com/burn-rate.html

Cartridge: 7.62 x 39mm Russian
Load Type: Rifle
--------------------------------------------------------------------------------

Bullet Weight (Gr.) Manufacturer Powder Bullet Diam. C.O.L. Grs. Vel. (ft/s) Pressure Grs. Vel. (ft/s) Pressure (first load is min second is max)

--------------------------------------------------------------------------------

125 GR. SPR SP Hodgdon BL-C(2) .311" 2.150" 30.0 2155 32,200 CUP 31.5 2349 38,800 CUP
125 GR. SPR SP Hodgdon H335 .311" 2.150" 30.0 2219 35,400 CUP 31.5 2408 40,900 CUP
125 GR. SPR SP Hodgdon H4895 .311" 2.150" 28.0 2171 29,900 CUP 29.0 2249 33,600 CUP
125 GR. SPR SP Hodgdon H322 .311" 2.150" 28.0 2210 32,900 CUP 29.0 2323 35,400 CUP
125 GR. SPR SP IMR IMR 4198 .311" 2.150" 24.0 2250 42,500 CUP
125 GR. SPR SP Hodgdon H4198 .311" 2.150" 24.5 2190 34,200 CUP 26.5 2378 40,400 CUP
125 GR. SPR SP IMR IMR 4227 .311" 2.150" 18.5 1995 44,100 CUP
150 GR. HDY SP Hodgdon BL-C(2) .312" 2.220" 27.0 1904 33,600 CUP 29.5 2090 40,400 CUP
150 GR. HDY SP Hodgdon H335 .312" 2.220" 27.0 2055 36,000 CUP 29.0 2132 42,500 CUP
150 GR. HDY SP Hodgdon H4895 .312" 2.220" 27.0 2080 33,600 CUP 28.0 2154 39,300 CUP
150 GR. HDY SP Hodgdon H322 .312" 2.220" 27.0 2084 34,200 CUP 28.5 2192 40,400 CUP
150 GR. HDY SP IMR IMR 4198 .311" 2.220" 22.5 2070 43,600 CUP
150 GR. HDY SP Hodgdon H4198 .312" 2.220" 22.5 1947 33,600 CUP 24.5 2122 39,800 CUP

R.W.Dale
March 6, 2009, 06:34 PM
Varget is slower than Bl-C2 by a goodly bit
http://www.reloadbench.com/burn.html

105. BLC-2 (Hodgdon)
117. Varget (Hodgdon)

JpWilly while applicable for the original cambering 7.62x39 data really doesn't apply to this new one except as a starting point with the slower propellants. If I was going to use 7.62x39mm loads I would have saved myself the trouble of reaming this chamber and continued to shoot 7.62x39. There's enough of an increase in capacity that top x39 charges require another grain or grain and a half of powder to achieve the same speeds. Hence me stepping up to slower propellants than I would have used before.

For 150grn bullets H335 is still a millitad too fast to achieve 100% load density, BL-c2 is so close to H335 there's really no difference 105 vs 108 on aburnrate chart . A compressed charge of varget is doing pretty good hitting hitting speeds just shy of 2300fps. With very little case head expansion. the same cannot be said for H335 or it's twin BL-C2

OH the joy of a wildcat! I'll get it figured out...eventually

db_tanker
March 6, 2009, 06:53 PM
has 4227 or Lil'gun made it to your testing yet?

I know Lil'gun is closer to that mag-pistol powder but still should be at least looked at.

I'd also take a look at mebbe using 748 as well.


D

jpwilly
March 6, 2009, 11:38 PM
Krochus, I realize the load data was not going to be a match it was posted FYI for other readers to see standard load data for the standard Russian cal. The burn rates listed by Hodgdon show BL-C(2) as being slower than Varget so why should we trust the Reloading Bench site more so than the manufacturer? The obvious answer is Hodgdon got it wrong but I want to know how or why you personally believe that. Hodgdon lists 335 at 66, Varget at 81 and BL-C(2) at 83...why the discrepency?

Schleprok62
March 7, 2009, 01:44 PM
Krochus: Nice post... cool thread... fun read, I know you're having fun with the testing... :)

As far as burn rates go... well, I have looked at a number of "reasonably reliable" sources and find that no two burn-rate charts are the same...

The chart I have printed out clearly states that burn rates are difficult to make absolute as there will likely be variables from lot to lot. But it lists H335 @ 82, Varget @ 91, and BL-C(2) @ 97...

I am by no means an expert on any of this. However, any insight and information posted here will be looked at from a student perspective...

gvnwst
April 26, 2009, 11:46 PM
So, krochus, you figured out the powder thing, and maybe gotten some loads chrono'ed?

R.W.Dale
April 27, 2009, 12:13 AM
So, krochus, you figured out the powder thing, and maybe gotten some loads chrono'ed?

Sorry but no I haven't even taken it back to the range. I'm waiting on a reply from Leupold on my scope having possibly konked out. To be frank I've been sitting out on the recent nuttiness in the shooting world and have been working on and spending money on my Jeep.

I'll drag this topic back up when I have more to report

kcmarine
April 27, 2009, 12:14 AM
You've gotta find out the long- range effectiveness of that cartridge... That'd be incredibly interesting, especially fired out of an AK that has been re- chambered.

R.W.Dale
December 12, 2009, 05:26 AM
UPDATE

velocity data for pet loads to date

125g Speer TNT----32.5g H-335= 2525 fps avg

110g Hornady V-Max-----33.5g H-335= 2740 fps avg

100g Lapua HPCE----27.8g N-120= 2867fps avg

my best group to date was 32.5g of H-335 and 110 v-maxes @.254" :D for 5 at 100

What I've found is with less than 5% change in case capacity there's no real improvement in ballistics within pressure limitations set apoun 7.62x39 loadings. Where the improvement lies is in case life and pressure holding ability with loads EXCEEDING SAAMI pressures. Before reaming my chamber real toasty x39 loads would produce noticeable expansion rings and frequent case timings. The much straighter PPC LARGO case shows none of these ill effects at the same pressure and velocity levels thus improving brass life and allowing for higher pressures.

Ridgerunner665
December 12, 2009, 05:44 AM
krochus,

You probably already know this, but I'll throw it out there anyway (just in case you don't)

Varget and Reloder 15 are always pretty close together on burn rate charts...but they vary back and forth on which is slower or faster burning depending on bullet weights and case capacities...

Just sayin...Reloder 15 might give you a little more (or a little less, but its worth a try)

Marlin 45 carbine
December 12, 2009, 10:26 AM
as #8, good post krochus.

Walkalong
December 12, 2009, 11:10 AM
Very cool. This is what happens when shooters get bored with what they have. A very creative bunch. :)

Ridgerunner665
December 12, 2009, 10:02 PM
I keep coming back to this thread and looking at that fire formed brass...

My mind is telling me there is something more to be gained there than simply better case life...I just can't quite figure it out though.

5% more capacity should give more velocity (with the right powder)...not to mention that the blown out case should be a more efficient powder burner.

Something just isn't adding up...It has to be the powder and/or primer. (I think)

I don't know anything about reloading the 7.62x39mm...I've burned up a lot of it in SKS's, but never reloaded it.

But I do...I keep coming back and looking at that formed brass, its trying to tell me something...LOL.

Uncle Mike
December 12, 2009, 10:09 PM
Good job krochus...keep us posted on your load developments.

Maverick223
December 12, 2009, 10:17 PM
Probably a stupid question, and there is no *good* reason to want to do it, but can you shoot 7.62x39 steel cased out of it?

:)

R.W.Dale
December 12, 2009, 10:23 PM
Probably a stupid question, and there is no *good* reason to want to do it, but can you shoot 7.62x39 steel cased out of it?

:)
Yes you can. Yes you can

Maverick223
December 12, 2009, 11:46 PM
Interesting, thank you for indulging my curiosity.

:)

scythefwd
November 3, 2012, 12:40 PM
Thread Necromancy...

Dale, I know you have already disassembled and sold of the stevens a long time ago. The topic of 7.62x39 AR's came up on another forum and about how they are always problemmatic. Would your 30 ppc largo potentially feed better from a standard AR magazine and eliminate the feeding issues that most x39 AR owners experience?

If you enjoyed reading about "The 7.62x39 bench gun is no more, I give you .30PPC Largo" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!