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  1. #1
    Really Senior Member GUTS's Avatar
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    6.5mm/.257 Roberts

    When I bought this Type 38 carbine I bought a new stock from Numrich(the old one is pretty bad)and went out to shoot. I loaded five rounds, loaded and fired, cycled the bolt and fired again, that's when I noticed the piece of brass on the ground didn't look right, it looked like this:

    After I got over feeling very stupid for not checking the rifle out better(thank goodness for the strength of the Arisakaicon action) I unloaded the rifle and went home to see what the deal was. I soon discovered that a number of 6.5mm Jap rifles had been rechambered in .257 Roberts. I did some measuring on the spent cases and found out it is a .257 Roberts. Since then I have shot the correct ammo through it and it does good, it will hit the 200 meter NRA rams every time from the rest. You would think that the .257" bullet would be a tight squeeze in a barrel made for 6.5mm(.2559")but it works, although it may be hell on the bore. I figured I'd post this so somebody else doesn't have to learn the hard way.
    Here is the 6.5mm Jap bullet:

    Here is the .257:


    Here is the rifle, untouched Mum and matching numbers(wouldn't you know someone would screw up a full Mum, matching rifle).









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    Advisory Panel Patrick Chadwick's Avatar
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    Impressive case photos. Obviously A1 case material. (BTW , who from? I would like to get some of those cases)

    And I find myself wondering - why do some people get completely twittipated if their headspace is a couple of thou over spec?

    Patrick

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  7. #3
    Really Senior Member GUTS's Avatar
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    This is the ammo.

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    .257 bullet a tight squeeze in a 6.5mm bore? I think you have it backwards. I'm quite surprised your getting any accuracy at all. A 6.5mm bullet measures .263-.264 dia. while a .257 bullet measures .257. Appearently your gun's bore is just tight enough for the lands to grip the projectile. If you were to shoot it over a chronograph you'd see a lot of velocity loss due to blow by from the undersized bullet. The .2559 measurement is actually the BORE diameter for a 6.5mm barrel not the GROOVE diameter. Get yourself a set of 6.5/257 dies and use the correct dia bullets and you will get better accuracy.

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    Really Senior Member GUTS's Avatar
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    Quote Originally Posted by vintage hunter View Post
    .257 bullet a tight squeeze in a 6.5mm bore? I think you have it backwards. I'm quite surprised your getting any accuracy at all. A 6.5mm bullet measures .263-.264 dia. while a .257 bullet measures .257. Appearently your gun's bore is just tight enough for the lands to grip the projectile. If you were to shoot it over a chronograph you'd see a lot of velocity loss due to blow by from the undersized bullet. The .2559 measurement is actually the BORE diameter for a 6.5mm barrel not the GROOVE diameter. Get yourself a set of 6.5/257 dies and use the correct dia bullets and you will get better accuracy.
    Your right, I was thinking backwards, anyway I don't plan on shooting it anymore but if I do I'll take your advice, thanks.

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    Quote Originally Posted by Patrick Chadwick View Post
    And I find myself wondering - why do some people get completely twittipated if their headspace is a couple of thou over spec?

    Because they haven't experienced what happens when things ARE out of spec.! Copper/brass cases were adopted in the "way back" because they WILL adapt to a less than perfect fit.

    A handy example:


    VC version of a 7.62x39 in a crudely converted Japaneseicon Type 38 rifle. (Fired case extracted from the rifle is shown on the bottom.) The case only APPEARS longer- optical "delusion"...

    Too tight is generally worse than too loose!
    Last edited by jmoore; 03-12-2011 at 05:31 PM.

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    That is a beautiful rifle! WOW!!! Get the ammo straightened out and then have some fun with it.
    Bill Hollinger

    We're surrounded, that simplifies things!
    1944 Willys MB

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