Arisaka: correct caliber issue

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Heir Kommt Die Sonne

Heir Kommt Die Sonne

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We picked this up earlier this week. It is just like our other one in 7.7 Jap and the 7.7 ammo fit in there and cycled so we went out to shoot it and the first shot freezed up the bolt. We ejected the non-fired cases from the magazine and tried getting the bolt open. We couldn't so we went home and today I pounded the bolt open and this is what I found.
The case had just fine pressure, the primer and head are not deformed, but it's the case neck that's expanded. We compared the bolts with our other one and they're the same length and dimensions. So I started thinking, if it's a original military bore (which it is), the bolt is the same, but the case had expanded by the neck than whatever the correct caliber is , it's a longer case than the 7.7 Jap.
All I know is the Arisaka's came in two calibers, 7.7 and a 6mm version. Is there a third caliber that I do not know about?
The different caliber chambering got me thinking so I grabbed a .308 case to compare and I discovered that the rims of the 7.7 and .308 are identical and fit in the bolt. The .308 is shorter than the 7.7 but a 30.06 would be longer than them both. So I think this rifle had been converted to 30.06 but I can't confirm it because I do not have 30.06 ammunition in the house.
Here are pictures so any of you can help me discover what the problem is.

IMG_0916.jpg
IMG_0917.jpg
IMG_0919.jpg
IMG_0918.jpg

1st Pic: The rifle itself
2nd pic: the expanded fired case
3rd pic: 7.7 Jap, our expanded case and a .308
4th pic: A .308 fits perfectly in the bolt.
 
LoonWulf said:
thats pretty normal for fireforming.....even when doing the right brass in the right chamber lol.
Click to expand...
we weren't fireforming, we were firing 7.7 Jap which we believed to be the right caliber but the case fire formed and we got sticky bolt. We need to know the correct caliber or whatever is going on.
 
Heir Kommt Die Sonne said:
we weren't fireforming, we were firing 7.7 Jap which we believed to be the right caliber but the case fire formed and we got sticky bolt. We need to know the correct caliber or whatever is going on.
Click to expand...
sorry, my reply was a little ambiguous.

In effect what you did was basically fireform a 7.7x58 round to what ever your chamber ACTUALLY is. Even tho you didn't know there was an issue till you pulled the case out.

Even if you KNEW what your chamber was and had the right brass, you'd would almost certainly end up with a rounded shoulder anyway. It usually takes a couple firings to get a sharp shoulder. Especially when moving that much material around.

I 100% agree, you need to know what your dealing with before messing with stuff again. I had a similar incident with an Arisaka a few years ago, tho I found the issue before firing the gun.....even have a highroad thread about it.
 
LoonWulf said:
sorry, my reply was a little ambiguous.

In effect what you did was basically fireform a 7.7x58 round to what ever your chamber ACTUALLY is. Even tho you didn't know there was an issue till you pulled the case out.

Even if you KNEW what your chamber was and had the right brass, you'd would almost certainly end up with a rounded shoulder anyway. It usually takes a couple firings to get a sharp shoulder. Especially when moving that much material around.

I 100% agree, you need to know what your dealing with before messing with stuff again. I had a similar incident with an Arisaka a few years ago, tho I found the issue before firing the gun.....even have a highroad thread about it.
Click to expand...

When I first saw this Arisaka, I knew it had been worked on because the metal parts are parkerized or ceracoated. It didn't occurr to me that it was caliber converted to something else.
 
Lots of Arisakas were rechambered to 30-06 back in the fifties and sixties even though the 7.7 is a little bigger at the case heads. The other caliber is 6.5, not 6. This thing sure isn't any of those. Chamber cast and a copy of Cartridges of the World is in order. BTW, the bore of the 7.7 runs around .312-.313, (groove dia). 30-06 is .308. You have a strange one. I sure wouldn't shoot it again until I knew what was the right fit.
I can recall reading the classified ads in the back of Sports Afield and the others "Japs, rechamber your 7.7 to 30-06, 6.5 to .257. I think it was $25. About 1960. The same time I was buying rolling blocks for $13, 1903s for 18, and Smith victory models for $25.
 
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30-06.

The bore is still 7.7, while not well known for accuracy with re-chambering....but it will work good, if the chambers lengthening been done correctly.

Its a simple reaming job to get the chamber from 58mm to 63, while the Thai did a lot, and the South Koreans did it by the thousands, a few were done state side.

Can we see a picture of the receivers top? Might have Thai, Korean or Japanese markings that can give us an idea of its path to 30-06.
 
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I might add that the Chinese in Northern China, made a version rechamberd/rebored to 8mm Mauser, 8x57.
An 8mm bore comes to .323, but squeezing a .323 down a .312 bore wouldnt freek the Chinese much.....LOL!! Its been done with Mosin's of the same diameter, so its doable in a pinch, like a war....

From what I see of the cases, Im still fairly sure its a 30-06.
 
My 7.7 keyhole with any diameter bullet under .311. .312 works best in mine, original, unmodified.
 
The Koreans scrubbed Mums, phosphated/parkerizd the finnish after shortening the barrel chamber end, for rechambering for 30-06.

Was named the US Rifle, type 99, Japanese, caliber .30

I would see if an '06 will chamber. The job might be botched with the shoulder looking the way it does, but, it may be that a 30-06 will fireform quite nicely.
Oh nice, I found my info page;
https://wwiiafterwwii.wordpress.com/2015/06/19/wwii-japanese-weapons-in-the-korean-war/

Most conversions made in the US didnt have the barrel shortend up and have a rather loose chamber to cartridge fit. Not enough to worry a person (Ive shot my friends Korean 99) but Japanese rifles are known for generous chambers.
 
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