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Old April 15, 2020, 06:56 AM   #1
Peter R
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.311 verses .312. 7.7 jap Arisaka

Good morning,
New member here, hope this post is in the correct location,
I have been reloading for many years, For many different cartridges , however recently acquired a 7.7 Japanese Arisaka, I received this gun from an old timer who has had it for many years, it was a war take-home From his brother, and has been fired many times while in his possession. I manage to find a couple of boxes of ammo for it and took it to the range. She’s a good shooter.
Then I started the process of tracking down some new brass and projectiles etc. But after looking at several reloading books, and reading countless articles my bore diameter came into question. So I slugged the barrel and it mikes out at .312 to .313 at the widest point.
Hindsight is 2020 they say. I fired off every round I had, I should have pulled one bullet and checked its diameter.
Does anyone know what the factory ammo bullet diameter is? Dose it truly matter whether I order the 311 versus the 312 Or even the 313, Or am I overthinking this?
Thanks
Peter
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Old April 15, 2020, 08:30 AM   #2
tangolima
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You can slug the barrel to find out. Unless you intend to win match and set record, there is not much difference between .311" and .312".

My 7.7 Arisaka was from an old timer coworker. His father served in the Philippines during the war. It had been sitting in his garage for decades before he sold it to me.

-TL

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Old April 15, 2020, 09:02 AM   #3
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There is a lot of difference in bullet performance in the Type-99 rifle . Certain brand and/or type bullets will shoot much better than others . Also the land dia is important , not just the groove . Also is your rifle an early chrome bore or a later non chrome bore ? That also makes a difference . My first choice would be the Hornady .312 150 sp bullet . If that one acts like it is too small with flyers or tilting at range , the next step would be the H .312 174 rn , it will rides straighter due to it's extra bering surface . Also with the chrome bore they tend to like a little velocity . The 7.7 is not like a .303 Brit , a lot closer to the 8x57 mm Mauser in loading .
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Old April 15, 2020, 01:02 PM   #4
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Quote:
The 7.7 is not like a .303 Brit , a lot closer to the 8x57 mm Mauser in loading .
If you're talking about the rimless case and loading it, then yes, it is more like the 8mm Mauser. But if you're talking load levels, powders, bullets and velocities, the 7.7 Jap IS the .303 British.

I went through my old manuals some time back, looking at this very question. Data for both rounds is either identical or 1 (one) grain difference, some had the Jap at 1 gr more as max, some had the Brit in that spot.

It's not often thought about today, but quite a bit of British "tech" and ways of doing things were adopted by Imperial Japan as it changed into a modern nation. They drive on the "wrong" side of the road. The Imperial Navy was patterned on the Royal Navy. A couple of the Japanese battleships we fought in WWII were built in Great Britain, (before the war) and the 7.7mm round was adopted to duplicate .303 British performance, in a rimless case.

Unless your barrel is grossly over, or undersized, the usual .312" bullets should work well enough. If not, then for accuracy, you need to look at cast bullets, sized for your bore.

Curious about your rifle, there were several variations during production, later war rifles having fewer features. Is your rifle still in "issue" condition? Does it have an intact "Mum"?

One other thing to be aware of, at this age, sometimes the multi part stocks will come "unglued". Even if the wood itself is still in good condition, sometimes the glue used has "died of old age". Not an "always" thing, just something to watch for, just in case. One of mine, had the forearm come apart during shooting, for just that reason. Nothing else wrong or damaged, and a simple repair, because of that.

I made my 7.7 ammo from .30-06 brass, and of course, after making a couple hundred rounds, found some new made 7,7 brass, so I bought a bag, maybe 2 I forget, now its been some time. I think I got it from Graf & Sons, but its been years, and I understand its not an "always have" item.

the one "iconic" accessory you need to look into getting is the bayonet. No longer cheap or plentiful, but its something the rifle "needs" to feel complete, at least for me.

Good Luck and enjoy the history!
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Old April 15, 2020, 03:36 PM   #5
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The 7.7x58 was made because the Japanese military wanted a 8x57mm round . They were already making 7.7mm bullets and barrels , so they just necked the 8x57 down to 7.7mm . They loaded it lighter to reduce the recoil for their smaller troops . If you use .303 Brit load data in the larger 7.7 case you will have light loads and could have some squibs . Squibs are a real danger in some 7.7 rifles as the chambers and throats can be oversized and some .303 used powders will not light correctly .The 7.7mm case has the same powder capacity as the 8mm , the same weight range of bullets , and the bullet dia is only .011 different . So any 8mm load is fine in the 7.7mm . That is what I have found in my test shooting of my over 200 Type 99 rifles in 7.7mm .
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Old April 15, 2020, 03:42 PM   #6
ernie8
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If I am not using 7.7x58 made cases the 8x57 case is my second choice . Much easier and makes better cases than 30/06 . Just run them in the 7.7 die enough to just let the bolt close , they will get a little longer when necked down , and load .
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Old April 15, 2020, 03:47 PM   #7
FrankenMauser
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.311", .312", even .313"... It doesn't matter.
Use what chambers and shoots, as long as you work up the load as usual.
(Don't go substituting bullets in established loads. Work it back up.)

I know quite a few people that don't even bother with .310/.311/.312/.313 for 7.7x58mm and 7.62x54R, because .308" projectiles work just as well, if not better.
(I use a variety in my x54R. Some .308s, some .312s, some .313s. If it works, it works. The upcoming 7.7 Jap projects will probably end up similar.)
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Old April 15, 2020, 04:19 PM   #8
Peter R
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Some good input here, I found the correct brass online and have ordered some. it was relatively inexpensive, this is not an early war 99, however it is probably mid To later war production. Not quite “ last ditch “ what got me a little concerned was when I referenced a few different load manuals, some listed The .311 projectile and others listed the .312 projectile.
This lead me down the path of researching on the inter-web..... We all know what kind of conflicting information you can find there... so I decided to slug the barrel. I guess my biggest concern would be firing say a .312 round down a barrel that was only .311, It’s only .001 of a difference,not sure if that can cause much excess pressure. none of the other calibers I’ve ever reloaded for listed two different diameter bullets. So it threw me for a bit of a loop.
I have several 8 mm Mauser‘s as well as an earlier model type 38 Arisaka, all very fine shooters.
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Old April 15, 2020, 05:02 PM   #9
ernie8
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With a .313 groove barrel a .311 or .312 will not may much pressure difference , not it can effect accuracy . Now if your only criteria is hitting a barn , a .308 to .313 will not matter much . The shallow Medford rifling of the T-99 has more troble gripping an undersized bullet , made worse if it is a chrome bore . Unless you use a .308 with a .303 Brit load of I-3031 in a rifle with a large chamber . Then you may not even hit the barn from the inside as you could have a powder meltdown and get a bullet stuck in your bore . That is a real problem with some loads and some T-99 rifles . A good , safe , mid range load is the Hornady .312 150 sp loaded with the whole crimp groove showing about the case neck , and 44.5 of I-4064 powder . Even though that load in a .303 Brit is above max in some manuals , it is a mid range load in the 7.7mm . What is the series and maker of your rifle ?
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Old April 15, 2020, 05:21 PM   #10
Peter R
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Ernie8 serial is 147Xx not sure about listing the last two numbers so substituted the with the xx
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Old April 15, 2020, 05:49 PM   #11
FrankenMauser
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He meant series. It's a letter prefix or suffix, accompanying the serial number.
Maker would be the production facility.

It doesn't matter much, though. Serialization was not always linear or consistent.
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Old April 15, 2020, 06:46 PM   #12
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The series mark is before the serial number , it is a Japanese character that represents a number . The maker mark is right after the serial number and is a logo for the maker . You can look both up on the net . Serialization was linear and consistent . With that information I can tell just when your rifle was made , by whom , and what features [ like the bore ] that your rifle has . The info would end up like : Nagoya series 6 serial # 14700
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Old April 15, 2020, 08:10 PM   #13
Peter R
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Sorry I miss read his reply. It looks like it is a type 6 with a Nagoya arsenal stamp on it.
Thanks
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Old April 16, 2020, 02:10 PM   #14
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From your description I kind of figured that was what you had . You should have the ladder sight , a pod band with no pod , no Dust cover , and you should have a non chrome bore . But they did seem to find an old chrome barrel now and then to use in that series , so that is not impossible . The load I gave you should work fine for you . You will notice a little case swell at the head after firing , that is normal . Good luck and have fun .
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Old April 16, 2020, 07:20 PM   #15
Peter R
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Thanks for the info..
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Old April 16, 2020, 07:39 PM   #16
rc
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.312 will probably be good. Even 32 mag pistol bullets in gallery loads. If you shoot jacketed ammo, you have a little more flexibility as you don't have to worry about leading. Don't overthink it too much.
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Old April 16, 2020, 07:54 PM   #17
ernie8
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I have shot the 32 mag bullets at over 3200 fps . They shoot a lot better then you would think , except for the one now and then that comes apart in mid air .
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Old April 17, 2020, 05:55 AM   #18
Peter R
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Strictly a jacketed round. Leaded up a barrel once. Rather not do it again. I am Consistently hitting steal plates out to 300 yards with my type 38, hope the 7.7 proves to be as accurate.
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Old April 17, 2020, 08:45 AM   #19
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Quote:
FrankenMauser wrote:
.311", .312", even .313"... It doesn't matter.
That may very well be the case. I never tested all that.

I started reloading mine with:
https://www.hornady.com/bullets/rifl...nterlock-rn#!/
They shot less than an inch at 100 yds and killed several deer.
Never tried anything else.
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Old April 17, 2020, 09:00 AM   #20
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Hmmm ...

Quote:
Originally Posted by 44 AMP
If you're talking about the rimless case and loading it, then yes, it is more like the 8mm Mauser. But if you're talking load levels, powders, bullets and velocities, the 7.7 Jap IS the .303 British.

I went through my old manuals some time back, looking at this very question. Data for both rounds is either identical or 1 (one) grain difference, some had the Jap at 1 gr more as max, some had the Brit in that spot.
vs.

Quote:
Originally Posted by ernie8
If you use .303 Brit load data in the larger 7.7 case you will have light loads and could have some squibs .
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Old April 17, 2020, 01:22 PM   #21
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Quote:
I went through my old manuals some time back, looking at this very question. Data for both rounds is either identical or 1 (one) grain difference, some had the Jap at 1 gr more as max, some had the Brit in that spot.
I wrote this based on my memory at the time, and have since gone back again and looked, and so I need to further expand/explain my statement.

With some powders and load levels the difference in the data is small but with others it can be 4grains or so at max, which is nearly 10% and therefore something considerable.

However, the "middle range" of the data for both rounds is an overlap. For example, with bullet and powder XXXX, data for the Jap might show 48gr as max and for the Brit show 44gr as max. If you're loading 42gr, so the same in both, that's what I call "overlap".

I've never heard of a problem with squibs (and what the heck is "powder meltdown??) but anything is possible if you're not loading correctly matched components and arms.
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Old April 17, 2020, 05:37 PM   #22
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After test firing over 200 T-99 rifles and having several other friends do the same with their's , we all ran into the same problem . It also happens on other military rifles . It is caused by several problems , and happens when all of them are present in a rifle . An oversized chamber , too small a case , too long in the throat for a bullet , too small a bullet , cold weather , and certain powders . What happens is when the primer goes off it pushes the bullet out of the case and it does not seal in the throat . The powder then just melts into a blob and the bullet is stuck in the bore . Some Type -99 rifles do this [ with some .303 loads ] and it is common in 8mm Lebel , 8x50 /56r and a few others . Listed loads do cause this problem . Hornady had this problem with some of their first loaded 7.7 ammo . As I showed you before the 7.7mm round is almost exactly the same as a 8x57mm , and the rifle is just as strong . I have test fires over 200 T-99 rifles with over 50 different loads and I can tell you for sure the bullet size does make a big difference .
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Old April 18, 2020, 02:16 PM   #23
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Quote:
It is caused by several problems , and happens when all of them are present in a rifle . An oversized chamber , too small a case , too long in the throat for a bullet , too small a bullet , cold weather , and certain powders .
I've only had a couple dozen "milsurp" rifles over the years (that stayed in "issue condition), and have never run into that "perfect storm" of conditions you describe.

That might be serendipity, or it might be that, combined with my loading practices, choice of bullets and powder.

I use bullets that are "right" for the nominal bore size (.311/.312", not .308" for 7.62x54R, .303 Brit and 7.7mm Jap, .308" for US .30s, .264" for the 6.5 Swede, .323" for 8mm Mauser, etc.), and for most of them I used IMR 4895, and loads from my old (1970s) Lyman manual. And CCI standard large rifle primers.

I can see where, if you load unusual combinations, you can get unusual results, but not doing that myself, I've never seen any.
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Old April 18, 2020, 07:05 PM   #24
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What bullet do you use for a Type-99 with a .316 groove , or a 8x57 rifle with a .326 , a 8mm Lebel with a .329 ? ? How do you deal the major part of the problem like the extra large chamber or leade ? Most military rifles do not have groove sizes in the standard US bullets sizes .264 , .284 , .311 , .323 and so on . Published loads can cause the problem . Using .303 Brit data with some powders in a 7.7mm will cause the problem . The load I gave the guy is a good , safe load . With limited loading experience , you may not have seen it , but the does not mean it does not happen .
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Old April 18, 2020, 07:25 PM   #25
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Calm down, little fella.
There's no need to try to establish dominance.
You're not the only person here that knows how to select a bullet for a particular groove diameter.
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