6.5 Jap, what is it now?

GUTS · Posted: Wed Nov 25, 2009 9:35 pm Post subject: 6.5 Jap, what is it now?

I just finished putting a new stock on an Arisaka Type 38 Carbine and put a cartridge in it for a test firing. The empty case came out slightly altered fron the original. I don't know how many of you guys have thought to cerracast a rifles chamber before you shoot it, but I haven't. I think by the looks of the empty case that this rifle is chambered in perhaps .257 Roberts as opposed to 6.5x50mm. I would think the brass case would serve the same function as a chamber casting as far as measurements go.
The rifle:

The ammo:

I was thinking of headspace on rimmed cases when I drew the measuring lines, the line should be at the bottom of the base.

Pumpkinslinger · Posted: Thu Nov 26, 2009 12:19 am Post subject: Re: 6.5 Jap, what is it now?

Wow! Glad it didn't blow and hurt you! What diameter is the case mouth opened up to? Are you sure that wasn't a 7.7x58mm rifle?

Vince · Posted: Thu Nov 26, 2009 12:56 am Post subject: Re: 6.5 Jap, what is it now?

WOE Guts...that is one close call mate. As Punkin said...Glad it didn't blow and hurt you.

I would most definitely be doing a casting of the chamber mate. The case has most likely expanded fully to the chamber size...but I would still be making a casting to be certain. A rough measurement of the case mouth size in the pics shows it to be about 1mm larger than the loaded round...also, you say you loaded it with 6.5x51R rounds...but Punkin asks if you are sure that it is a 7.7x58mm rifle. The question I would ask is...are you sure that you have the calibre right for the factory chambering?

Let us know what you have found out mate...I'm real curious on this one.

Cheers, Vince

SwampFox · Posted: Thu Nov 26, 2009 6:36 am Post subject: Re: 6.5 Jap, what is it now?

Guts,
Many Japanese rifles were converted in the US after being brought home by GIs when WWII was over. The Ariaka action is extrodinarily strong, if the gun was made prior to or in the early years of the war. All 38s are early guns as the Japanese changed to the type 99 just prior to the war. The stories of Ackley trying to blow Arasaka actions are legend. Example, a 6.5 type 38 chambered to 7.7 and fired with the original barrel, without ill effect.

The 38 type guns are 6.5x51 many were converted to 6.5 x 257 which appears to be what you have. Note that the chamber is now different but the 6.5 barrel is original. You have a close enough cast of the chamber in the fired case. Check these deminsions for the 257.

Base (bottom of rim) to base of neck aprox 1.912
Base to bottom of shoulder 1.728
Top of rim to base of neck 1.864
Bulge diameter above web slightly smaller than .472
Exterior neck diameter .288 (sized diameter w bullet so will be larger in fired case)
Base of shoulder diameter .430

The number will not be exact but should be close.

If you reload you could make your own die set up by anealing a 257 Roberts sizing die and then cutting the shoulder off with a mill. This die would be used to rersize the base of the brass as needed after fire forming. With a 6.5 Arisaka die set you could back the sizing die out and resize the neck for neck sizing. You would also use this die to expand the neck of the 257 to 6.5. Then use the seater to seat the bullets. One thing of importance is that the angle of the shoulder is 20 VS 20.45, about the same, so unless the .013 shoulder diameter difference proves to be a problem you should be able to neck size the brass. Fire forming will be a snap, as you have already seen.

You might also be able to find a 6.5x257 die set.
Best,
Ed

SwampFox · Posted: Thu Nov 26, 2009 7:06 am Post subject: Re: 6.5 Jap, what is it now?

Guts,
My old brain is just a tad slow. But, it usually gets there given enough time. The 257 Roberts is basicly a 257 x 7x57. So if you neck up the 257 to 6.5 you will have something very, very close to a 6.5x57 with a slight shoulder angle change from about 17 degrees to 20 degrees, but the rest of the deminsions should be OK to load the round with the 6.5x57 dies. Look here:

chasse-tir.ifrance.com...uilles.htm
www.grafs.com/metallic/1975

Have a nice turkey day.
Best,
Ed

Pumpkinslinger · Posted: Fri Nov 27, 2009 3:09 am Post subject: Re: 6.5 Jap, what is it now?

I'm just looking at the case mouth of the fired case. It appears to be larger than 6.5mm.

SwampFox · Posted: Fri Nov 27, 2009 7:22 am Post subject: Re: 6.5 Jap, what is it now?

Mike,
The barrel on the gun in the photo is an original type 38 barrel. While it could be rebored, I doubt anyone would spend the time to rebore a Japanese barrel at the time the conversion was done or now, for sure.

I bought my first Arisaka for $5.00 probably about the time this conversion was done. Until recently the guns were not worth much.
Best,
Ed

POP!! · Posted: Fri Nov 27, 2009 11:27 am Post subject: Re: 6.5 Jap, what is it now?

That is NOT chambered in 6.5x51R!

fnuser · Posted: Sat Nov 28, 2009 2:19 pm Post subject: Re: 6.5 Jap, what is it now?

the conversion to 6.5.x57 is a common one and that would be the third one I know of the other 2 were seen in person. Run a slug down your bore and give us a groove to groove dia?

GUTS · Posted: Sat Nov 28, 2009 3:31 pm Post subject: Re: 6.5 Jap, what is it now?

fnuser wrote:

the conversion to 6.5.x57 is a common one and that would be the third one I know of the other 2 were seen in person. Run a slug down your bore and give us a groove to groove dia?

The barrel is original so I guess it would be whatever the 6.5 Jap is. It's too bad that this rifle is altered, the bluing is almost perfect, the #'s match, and it has an untouched Mum.

terry264 · Posted: Sat Nov 28, 2009 9:21 pm Post subject: Re: 6.5 Jap, what is it now?

Hope that came thru, from ammoguide.com,,,,great site.

PaulS · Posted: Sat Nov 28, 2009 10:56 pm Post subject: Re: 6.5 Jap, what is it now?

The barrel could be the same one but it may have been rebored to a larger size. Run a plug through it to be sure or have a smith look at it to be sure.

Pumpkinslinger · Posted: Sat Nov 28, 2009 11:20 pm Post subject: Re: 6.5 Jap, what is it now?

What does the "new" case mouth measure?

terry264 · Posted: Sun Nov 29, 2009 3:09 pm Post subject: Re: 6.5 Jap, what is it now?

If the original barrel is indeed a 6.5 and in good shape, it also has 1:9 twist and would be an easy conversion to 260 rem. Just a thought.

fnuser · Posted: Mon Nov 30, 2009 8:32 pm Post subject: Re: 6.5 Jap, what is it now?

not any more the 6.5 x57 is a great cartridge but the shoulder is farther forward then the .260 his measured photos reveal this. I bet if he slugs it he'll find his groove dia is closer to .262" then .264". If he tried to .260 it without setting it back he'll have a severe case of excessive headspace. (pun intended)