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Old November 3, 2012, 12:33 AM   #1
akinswi
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7.7x58 jap ammo

Ok I have two cases here both stamped 7.7x58 jap graf, which I think is hornady, and the other is stamped 7.7x58 jap PPU which is priv. Now my question is why does the graf look way diff than the ppu? the neck and shoulder are completely diff... the brass length is the same but if you looked at them side by side you would say they look like completely diff rounds/caliber any suggestions why this is? They both shoot fine but I notice the PPU theres a little blow back from the round due ot the shorter neck and sligther shoulder. Again this isnt somebody necking down 30-06 or what ever , they both from factory stamped 7.7x58 jap but they sure dont look the same.
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Old November 3, 2012, 01:16 AM   #2
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pictures might help out a little with explanation, of both rounds side by side and the boxes.
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Old November 3, 2012, 01:31 AM   #3
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here is a phote attached
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Old November 3, 2012, 01:46 AM   #4
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photo 2

here are the boxes it came out of, one box head stamped 7.7x58 jap graf and another 7.7x58 jap PPU. again same exact box brand new from store but brass size is different
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Old November 3, 2012, 01:51 AM   #5
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photo 3

see the diff between the two cases, again brand new out of the box I dont understand the diff?
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Old November 3, 2012, 01:53 AM   #6
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They look like they were fired in a .30-06 chamber and one fireformed more than the other.

Do you have a couple of unfired cartridges to compare? I imagine they'll look the same.

Has your Arisaka been rechambered?
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Old November 3, 2012, 01:59 AM   #7
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sport, i dont know i bought it a local gun shop. they couldn't have been fired formed from 30-06 brand new out of the box.
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Old November 3, 2012, 02:03 AM   #8
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photo 4

I dont have any rds left with the shorter neck, but here are some brand new rds to compare again these all came out of same box brand new, I have only fired these once.

But I did compare the shorter neck case to an 30-06 case and the shoulders identical, the neck just has been trimmed down, im baffled, may the manf ran out of 7.7 brass and just necked down a 30-06 case. remember these were brand new rds
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Last edited by akinswi; November 3, 2012 at 02:09 AM. Reason: more info
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Old November 3, 2012, 02:12 AM   #9
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they are not NIB.
hornady has their own head stamp. also if I understand you correctly you only purchased the brass and the boxes state a bullet weight, only found in preloaded ammo. what you bought was somebodies used brass which they reboxed and sold to to your local gun store. I will agree with the assessment that one was mistakenly fired from a 30-06 and the casing fire formed out to the chamber dimensions while the other appears to have been fired from the proper chamber.

EDIT: I just re-read the original post. you say that the PPU/PRVI blows back?

stop firing at once and take it to a gun smith to verify chamber.
I will almost bet that your rifle was bored out to 30-06.
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Old November 3, 2012, 02:20 AM   #10
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so your saying they reloaded somebodies used brass, and boxed in a hornady box, because I bought the box of ammo, not brass....

also for **** and giggles, I put an empty 30-06 brass and wahla!!! it fit and bolt closed, you both were right. This is a plus because as you can see a box of that jap ammo is not cheap and I have loads of 30-06ammo and components to reload it with.

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Old November 3, 2012, 03:04 AM   #11
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No, that's not what I was saying. The ammunition in question is proper 7.7x58 Arisaka. Your gun has been rechambered for .30-06.

Will .30-06 fit in the magazine? If it does the gun has had some proper work done to it. If only the chamber is modified you have a bolt action single shot.

I'd have the headspacing checked to be sure everything's okay for that round. The 'smith should also stamp the appropriate chambering information on the barrel while he's at it.

7.7x58 is a shorter round than '06. Because of the long bullet jump there wasn't a whole lot of pressure needed to get the bullet out of the case. After that, there wasn't a whole lot of pressure difference between the inside and outside of the case since you didn't get a good seal at the neck. One brand of case was harder that the other and didn't stretch as much.
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Old November 3, 2012, 03:13 AM   #12
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yes 30-06 does fit in the magazine, bolt cycles cleanly I put a live round and cycle bolt no issues, but the bullet diameter for 30-06 is .308 and for 7.7 its .311 wont this make a difference?

im also going to gun smith tomorrow to pick up another firearm, i will have him check it out and make sure it is chambered for 30-06 or for 7.7x58.

Last edited by akinswi; November 3, 2012 at 03:24 AM.
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Old November 3, 2012, 04:53 AM   #13
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You'll probably want to slug the bore. Mine is 0.313" but shoots Hornady 174gr .312 bullets well.

If your gun is a rechambered 7.7 it will probably shoot .308 bullets okay (if 3-4" at 100 yards is acceptable). If it was mine I'd load .312 bullets in .30-06 cases.

If you load .312 bullets MAKE SURE the neck area of the chamber is not pinching the loaded cartridge by painting a loaded round with magic marker and inspecting it for drag marks and such after chambering it a couple of times. Arisakas are tough, but not that tough.
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Old November 3, 2012, 07:33 AM   #14
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One other thing you need to know...

The Arisaka round is slightly larger at the base, so unless the barrel was set back, the chamber is going to be oversized, meaning your .30-06 brass will swell at the base. Not a good combination for long-term case life.
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Old November 3, 2012, 05:55 PM   #15
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I don't know who shot John, but I do know that that 7.7 case was fired in a .30-'06 chamber. I have a bunch like it that I fired in a M1903 Springfield to check out stories by WWII vets that they could fire Japanese ammo in the American rifle.*

As to the cases being "brand new", the labels clearly show they came from a reloading shop, so I think they got something mixed up someplace. Maybe they put a returned box back on the shelf without checking, I don't know. But there is no way a factory produced those short neck cases. Period.

Jim

*I did just that. No sign of any excess pressure, no sign of any significant case swelling, and even the clips work just fine!

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Old November 3, 2012, 10:01 PM   #16
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I don't see anything wrong with the ammo from the Hornady boxes. Hornady probably doesn't make their own 7.7x58 brass so different lots having different headstamps really doesn't surprise me. The boxes do, however, look pretty worn for being new off the shelf.



In any case it appears all the fire forming was done in the OP's rifle. 7.7x58 has a shorter neck than '06 but the really short necked fired case is a result of the 7.7 being fired in a .30-06 (or other) chamber. We really don't know what the OP's rifle was rechambered to, only that a .30-06 will fit....

'06 is a good bet though since it was a common conversion for a bring-back rifle with no local ammunition availablility.

The case on the left fireformed more because it was softer. The one on the right didn't fireform much at all. Or maybe the one on the left just had a better neck seal, who knows.
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Old November 3, 2012, 10:55 PM   #17
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" I have a bunch like it that I fired in a M1903 Springfield to check out stories by WWII vets that they could fire Japanese ammo in the American rifle.* "

The stories I have always heard is that the Japanese could fire .30-06 ammo in their Arisakas.

Load of kitchen crockery.
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Old November 4, 2012, 12:44 AM   #18
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Nope, it won't work the other way. I had heard both stories years ago, and thought the same as you. Then I heard the "7.7 in Springfield" story from a source who is almost always accurate and decided to try it. I admit to being a bit surprised at the result. Not only did the 7.7 (Norma) rounds load from the Japanese clip but it fired fine and I could not tell it from the .30-'06. I fired 20 shots and got a 100 yard group of about 6 inches. (I checked with the scope, I didn't pick up the target.) With my aging eyes and iron sights, and wrong ammo, I thought that was pretty good.

Two points of interest. The "oversize bullet" (.311 vs .308) did not blow up the rifle, cause the bolt to come back into my head, or wipe out the county. There was, in fact, no sign of any significant pressure increase; the primers looked quite normal.

The supposed case swelling didn't happen either, nor did it with reworked .30-'06 fired in a Japanese rifle. The base dimension for the .30-'06 is .470 +/- a thousandth or so. The base dimension of the 7.7 Japanese is .471 again +/-. In practical terms, they are the same. So blown cases, bulging brass, go the same route as other myths.

There is probably some confusion from the fact that the Japanese used three different 7.7mm cartridges.

1. The rimless 7.7x58, which we are discussing. It was used in the Type 99 rifle and the Type 92 light machine gun.

2. The 7.7 semi-rimmed was used in the Type 99 heavy MG, a Hotchkiss type; the feed strips are around at gun shows occasionally. Some folks buy them thinking to use the ammo in their rifles; won't work.

3. The thrid 7.7 round is rimmed; it is simply the .303 British made for use in the Japanese Navy's licensed copies of the Lewis gun.

Jim
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Old November 4, 2012, 07:15 AM   #19
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I could swear I have something around here, and I'll be darned if I can remember what it is or where it is, that indicates that the nominal base diameter of 7.7 military rifle ammo to be closer to .480 than .470...

I know the .311 bullet isn't an issue. if anything, that will raise pressure a few thousand PSI, if any at all, from the nominal working pressure of the cartridge, and IIRC the nominal working pressure for the 7.7 is 54,000 PSI, while for the .30-06 its closer to 65,000 psi, so there's a lot of inherent leeway.

Oh, by the way, I've seen several Arisakas over the years that would chamber the 7.7 semi-rimmed ammo out of the feed strips. Don't ask me why or how.
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Old November 4, 2012, 09:44 PM   #20
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I rarely agree with Mike, but the base difference is quite wide between an '06 and a 7.7, depending on who's brass you use. Winchester is one of the smallest cases made. Grab a handful of different brands and mike the bases on unfired rounds. If you would take a small case (Such as Winchester) and use it in an Arisaka with a max chamber, it could rupture if loaded hot enough. I recently sold an Arisaka at an auction that was re-worked to 30-06 by the U.S. Military during the Korean War. It had all the stampings and was the weird phosphate green. The difference is that military brass is large and quite heavy compared to commercial brass. Pretty much the rupturing starts as the loads increase. I once fired a factory .300 Savage in a 7.62x54R chamber (Long story) and the brass looked normal. The factory loads are usually quite light. On the other hand, there are many people that were not so lucky with unsupported cases in the wrong chamber. The original poster was not too clear, but I think he said both cases were headstamped 7.7 JAP. The shorter one was just loaded lighter and did not expand.
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Old November 4, 2012, 10:02 PM   #21
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No, the base runs just what I said; in reloading 7.7 Jap, the .30-'06/.308/8mm Mauser shell holder is used. But I will clarify my non-interchangeable statement a bit. The 7.7 semi-rimmed will fit into the 7.7mm rimless chamber but the rim won't fit into the bolt face of the Type 99 rifle. So it won't feed from the magazine, and if it is dropped into the chamber the bolt cannot be closed on it so it can't be fired.

The 7.7 rimless rifle cartridge apparently will feed from the strips, but I have been told that the gun will be unreliable because the extractor won't always grab the smaller rim. I cannot test this condition, as I have no Type 99 HMG handy, so I am going by what I have read.

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Old November 4, 2012, 10:53 PM   #22
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I've used a lot of reformed '06 cases from M2 ball in my 7.7 and can say that it does swell a bit above the web. I generally use them twice and then put them in the recycle bucket.

I've heard people swear they've run surplus '06 in their Arisakas but I have a hard time believing it. I tried and couldn't force an empty '06 case into mine. Well, I suppose I could if I was willing to take a hammer to the bolt...

The slot in my Type 99 is a little too wide for '03 clips, but they'll work if you don't get in a hurry. Arisaka clips (I wish I had some) might be too wide for loading a '03 rifle.
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Old November 5, 2012, 06:47 PM   #23
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The clips are not identical, one difference being the position of the lugs, and the fit in the other rifle is not perfect, but will work.

Of course, firing .30-'06 in a 7.7x58 chamber is impossible for the reason you mention. It would take a big hammer.

FWIW, there is only one Japanese rifle clip; the 7.7 and 6.5 use the same clip.

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Old November 5, 2012, 07:24 PM   #24
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When is the last time someone here reloaded original Japanese 7.7 brass? No argument there.
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Old November 5, 2012, 10:11 PM   #25
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Unfortunately I don't have an example of a Japanese military 7.7 rifle round in my collection.

"The 7.7 rimless rifle cartridge apparently will feed from the strips, but I have been told that the gun will be unreliable because the extractor won't always grab the smaller rim. I cannot test this condition, as I have no Type 99 HMG handy, so I am going by what I have read."

The Type 99 was a magazine fed light/medium machine gun. The Type 92 was based on the Hotchkiss pattern and used the 30-round clips.

I have, around here somewhere, a 30-round clip for the Type 92.
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