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7.7 jap/06?

3K views 10 replies 7 participants last post by  Kody24 
#1 ·
I was on the phone with a friend of mine tonight and he asked a question I'm not sure I can answer.
he gave his brother an arisaka rifle he had and his brother managed to find some factory ammo for it, but....
He believes the barrel has been backed out a thread because the rifle chambers and fires 30/06, he handloaded for it with 06 brass and 7.7 bullets. he isn't sure if it's still safe to fire with the 7.7 arisaka ammo.
I'm confused how one ends up in this situation. I looked in my manual and there is the better part of 1/100th of an inch difference from base to shoulder between the two cartridges, so there may be a slim chance that the firing pin might not be able to strike the primer enough to hit the anvil and fire with the 7.7, at the same time, if it does fire that seems like a lot of space for the brass to expand, except that as a fan of P.O. Ackley I know that it should handle that expansion safely, otherwise the "fireform magnums" Ackley came up with would all blow up in your face.

Any suggestions on whether the gun should be fired with the 7.7 ammo, or if he should either stick with the 06 based handloads until he can make an appointment with a gunsmith?
 
#2 ·
Measure the fired brass from the 06 rounds and compare them to 7.7 unfired cases. If the gun has be rechambered to 06-7.7 then why would you want to fire 7.7 Jap ammo in the gun? The 7.7 ammo is much more expensive then the 06 based rounds. If the barrel is backed out a spacer would be needed or you would see a gap between the barrel and receiver. Be careful if you do not know exactly what you have. These are high pressure rounds and even though the gun is strong things can go wrong. A chamber cast is also a good idea.
 
#3 ·
I,ve had several rechambered 99,s to 3006 cases and they will shoot a standard 7.7 if you thumb the round into the magazine and bring it up with the bolt as the case rim goes into the extractor and that holds the case back against the bolt face allowing the firing pin to hit the primer. I saw it done several times, but I would not do it. get the chamber cast and be safe not sorry.
 
#4 ·
I agree with Guns - this rifle need a chamber cast.

Regardless of what caliber the rifle WAS - and especially if there is the slightest doubt - the rifle MUST be checked to determine the proper caliber. Further - only fire ammunition that is the CORRECT ammunition for that rifle, and if that rifle has been inspected and found safe by a competent gunsmith.

Back in the 1960s there was a giant craze to convert former military rifles into 'sporters'. Many companies sold all sorts of tools (including chambering reamers) to "garage-gunsmiths" (who didn't really know what they were doing or how to properly use those tools). The end result was sometimes a very dangerous rifle. An example is the fellow who cut a .30-06 chamber in a Japanese 6.5 Arisaka (and did nothing to the 6.5 diameter bore!). This man actually FIRED the rifle - if you can imagine the chamber pressure that was generated!:eek::eek::eek::eek::eek:
 
#7 ·
More than likely, instead of "the barrel was backed out", an aught-six chambering reamer was run into the chamber. This would allow you to shoot easily-available-and-cheap 30/06 in it. Accuracy would likely not be the greatest, since you'd be sending a .308 bullet down a .313 bore, but it would go bang and kill at deer at a couple hundred yards.

And I agree - if in doubt, do a chamber cast.
 
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#8 ·
Pretry much what I figured. He has fired the rifle, handloading. 310 or.311 bullets (I suck at remembering numbers) in o6 brass, and it was pretty accurate. He says some of them were a little hard to chamber. I think I'll start by getting a spent brass from the gun and measuring it out, then con him into casting the chamber. The guy is the biggest cheepskate on the planet and won't spend a dime if he doesn't have to, so it will take some convincing.
I think if I can get the true measurements for the chamber and find the actual distance to the lands, I should be able to come up with an 06 based cartridge that will chamber properly and figure out a proper oal and trim length. Then come up with a safe load for it. It's actually starting to look like an interesting little side project.
 
#11 ·
I haven't messed with it yet. He has the correct diameter for the bore, I just don't remember what it was. His concern when he came to me was the potential for excessive headspace with 7.7 factory ammo because it would use 06 brass. I talked to him a bit more about it, and he was using 30\06 dies and brass and just putting the 310 or 311 bullets in with those dies. He said that if he didn't trim the brass it was hard to close the bolt. With just that info, and knowing that the gun is in its original form, stock, sights etc, I'm betting somebody reamed the chamber out like Alpo suggested.
Apparently he figured out the 06 brass would work by taking an 06 round, putting the bullet in the muzzle to verify that ithe was undersize, then chambering it, ratchet strapping the gun to a tire, and pulling the trigger with a string. When the gun didn't turn into scrap metal he slugged the bore and proceded to load for it with 06 brass and dies and the proper bullets.
Yes, this guy is the source of many of the oddball questions I ask on here on occasion. I had to explain to hold mast night that even though 06 and 45acp have the same case head and body diameter the internal construction of the rifle brass would not permit him to take his 06 brass with cracked necks and turn it into 45acp brass to save money. He also informed me that he had not had any breakthroughs in his quest to swage penny's into bullet jackets.
Verry good friend, verry verry cheep friend, with lots of crazy ideas about how to save money on everything. He is actually the guy who got me into reloading but I turned my attention into learning everything I could about it, and into loading bulk on the cheep, while he concentrated on coming up with theories on how to squeeze his shooting budget down as small as possible while increasing what he could do. I provide the common sense to keep his guns, appendages and face intact.
 
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