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What load mimics the 7.7 Jap as far

Arisaka, Murata, Siamese, Korean, and North China Rifles
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S.B.
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What load mimics the 7.7 Jap as far

#1 Post by S.B. » Sun Dec 03, 2017 1:00 pm

as bullet weight and velocity of WWII Japanese issue ammo?
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Re: What load mimics the 7.7 Jap as far

#2 Post by Rapidrob » Sun Dec 03, 2017 4:57 pm

The 7.7 Jap is a rimless .303 Britt. Any load from 150-185 shoot very well. I use a true .312 180 grain bullet over BL-(C)2 and it is amazing at 800 yards.
Any load for the .303 Britt will work well, but the heavier bullets shoot the best.
The Jap rifles are very underrated and shoot much better than you'd think.
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Re: What load mimics the 7.7 Jap as far

#3 Post by slowbob2 » Wed Dec 06, 2017 8:39 am

The 7.7 J is nothing like the .303 Brit , other than using a bullet of similar diameter . The 7.7 mm has 15 % more case capacity , so a .303 load is too light . The case has a totally different shape . After test shooting over 250 different 7.7mm Arisaka rifles , I have found the Hornady 150 sp to be the most accurate bullet by far . Since the groove dia can be as large as .315 , boat tail bullets tend to shoot poorly in most . If your rifle has a really large groove dia the Hornady .312 174 rn bullet is the best . The chrome bore with the shallow rifling is also a reason boat tails do poorly . The chrome also tends to shoot better as the velocity goes up , velocity you will not get with a too light .303 load . In reality the 7.7x58mm is the same as a 8x57mm , almost the same case shape , size and the bullet dia is within .011 . So close that 7.7mm can be made by running 8mm into the 7.7mm die . Any military rifle will shoot a bullet 800 yards with no problem .

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Re: What load mimics the 7.7 Jap as far

#4 Post by nrobertb » Wed Dec 06, 2017 1:51 pm

On the old old forum there was an article about using 8mm Mauser cases in the 7.7 Jap. This is what I've been doing because I had a lot of extra cases on hand. Fireforming bumped the shoulder up a little and gave a slight bulge on the lower sides. The sizing die will remove the bulge but I just neck size to avoid overworking the brass.

The neck is a bit short. It works fine with jacketed bullets but I've had a lot of blowback with lead bullets.

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Re: What load mimics the 7.7 Jap as far

#5 Post by Smokey » Wed Dec 06, 2017 5:55 pm

I believe the velocity was around 2400 fps, which would put a 175 to 180gr bullet I the same performance as the .303 British. Check reloading manuals or try this:
http://www.hodgdonreloading.com/
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Re: What load mimics the 7.7 Jap as far

#6 Post by slowbob2 » Wed Dec 06, 2017 7:21 pm

That really has nothing to do with load data . .303 load data is not close to correct for the 7.7 mm . Any modern full power 8x57mm load data is also correct for the 7.7mm .

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Re: What load mimics the 7.7 Jap as far

#7 Post by slowbob2 » Wed Dec 06, 2017 7:23 pm

I looked up the load data in the link . It is way too light .

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Re: What load mimics the 7.7 Jap as far

#8 Post by ammolab » Wed Dec 06, 2017 8:26 pm

NORMA load data will get you GI velocity:

https://www.norma.cc/en/Ammunition-Acad ... -Japanese/

Hornady manual has data for 174gr bullets at 2400-2600fps for IMR & other powders

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Re: What load mimics the 7.7 Jap as far

#9 Post by Rapidrob » Thu Dec 07, 2017 6:16 pm

http://www.chuckhawks.com/303British.htm
http://www.chuckhawks.com/7-7mmArisaka.htm
The two cartridges are almost identical in performance. I've been using .303 Britt loads for decades with no issues what so ever.
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Re: What load mimics the 7.7 Jap as far

#10 Post by slowbob2 » Thu Dec 07, 2017 9:33 pm

Chuck Hawks is not a very good source for military rifle load data , or even history of said . End performance has nothing to do with load data of two very different cartridges . I was explained to you why they are different , sorry you do not understand .

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Re: What load mimics the 7.7 Jap as far

#11 Post by Rapidrob » Thu Dec 07, 2017 10:14 pm

I've been reloading for 55 years now. Nothing I load is unsafe,nor would I post such things. Lets leave it at that.
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Re: What load mimics the 7.7 Jap as far

#12 Post by ammolab » Thu Dec 07, 2017 11:41 pm

slowbob2 wrote:
Thu Dec 07, 2017 9:33 pm
Chuck Hawks is not a very good source for military rifle load data , or even history of said . End performance has nothing to do with load data of two very different cartridges . I was explained to you why they are different , sorry you do not understand .
But you don't think 8x57 is a "different cartridge"??? There is plenty of ACTUAL 7.7x58 load data available. Use it or you are just guessing.

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Re: What load mimics the 7.7 Jap as far

#13 Post by slowbob2 » Fri Dec 08, 2017 7:59 am

Just because you have been doing something for 50 years does not mean you are the best at it , or even understand it . I have been running for 50 years but still can not win the 100 meter dash . People that have been driving for 50 years are the best customers at one of my business's , the body shop . After 100's of different loads fired in over 250 different Type 99 rifles I am not guessing . A lot of published 7.7mm load data is just that, guesses , they never fired a real rifle or just one [ Lee's is a perfect example , just made up with no real shooting and in the real world their load data is not even close to what they say . ]. So it is poor . Due to size , shape , volume and pressure limits the 7.7 and .303 are very different . Since the 8mm and 7.7 have almost exactly the same size , shape , volume , and pressure range , with the same weight bullets the load data is interchangeable . 7.7mm can be shot in 8mm rifle , 8 mm cases can be used to load 7.7 mm . I do not care if rapid loads what ever , but other people looking for answers may like some good info .

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Re: What load mimics the 7.7 Jap as far

#14 Post by ammolab » Fri Dec 08, 2017 4:36 pm

Yes Lee data is poor. But 7.7 Jap is a .312" bore and 8mm is .323". Bore Size does matter in internal ballistics, and pressure curves will vary in similar size cases with different bore diameter bullets. A 150gr 270 Win will have a different load, a different pressure curve, than a 150gr 30-06 using the same exact same powder type/weight load. This with the EXACT same case.

Sure .303 is different, but a smaller case and same size bore make it a safer reference. 8mm is different in not such a good way, and just because you do it and survive does not make it "good info". As I said earlier, NORMA and Hornady make 7.7 ammo and have tested data. Anyone who loads ammo and can't afford or bother to buy a proper reference book needs a new hobby.

As an example: Hornady shows 48.2 gr of IMR3031 as a MAX 8mm load with a 150gr bullet (2800fps)

The max 7.7 Jap load for a 150gr bullet is ONLY 41.1gr of IMR3031 (2700fps). Enough for me to disagree that any 8mm load is safe and propper for 7.7Jap loading

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