Arisaka Type 38 pressure issues

HIGHRPM

HIGHRPM

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Hi guys. I just recently to my Type 38 carbine to the range to shoot it for the first time with some light reloads. While the gun shot great and printed on paper quickly, I noticed a couple of things when I checked the cases. The case body was bulged just above the head, which I think is due to a generous military chamber, and the primers looked like they were showing signs of pressure, flattened and trying to push out ,which I have never had before. I tried two of my lightest loads and both gave the same issue, so I stopped shooting. I have checked everywhere, but it seems no one makes a headspace gauge for this caliber. So, what can I do? Can I try a couple of different bolts, do I try loads that are even lighter than those in the manuals ? I shoot all my milsurps, so I have to try and fix this issue, so any guidence will be greatly appreciated, as always ! For what ever reason, I am not allowed to post a pic ?? :confused:
 
I have fired four Arisakas in the past year, all did the same thing with Norma ammunition ( 3 x Type 38s and a Type 99). Im not sure what causes it, but remember that the Arisaka action is one of (if not THE) strongest action ever built. Have you fired factory ammunition? if so what are the results? is your rifle matching? what is the condition of the bore/chamber area?

Also if you email me the pictures I will post them for you. There is a sticky in the photo section showing users how to do it.

:cheers:
 
Could be low-pressure ammo.
The primers stick out because the cartridge is not held tight against the bolthead then pressure builds up and rivets the primers flat. Seen very often with old 30-30s.
PP.
 
PP is 100% on this.

As far as THE BULGE is concerned, there is nothing you can do about it except make a new barrel.... and then you rifle won't be original any more: I don't know of anybody making 4-groove Metford barrels.

As far as the primers are concerned, you are shooting low-pressure loads and they DO like to back out the primers because the firing-pin pushes the whole thing forward into the chamber and fires the primer, the powder lights and makes pressure..... but not enough to slam the casing back against the bolt-face. Instead, the case adheres to the chamber wall (as it is supposed to) but there isn't enough pressure to stretch (and wreck) your brass. So the primer pops back, dimples and otherwise looks as if it has contracted a terminal case of leprosy or something.

If you want to change the situation, fire-form your brass with Ed's Famous O-Rings (or pony-tail ties: cheaper) and medium loads. RELOAD with whatever you like: the fireformed brass now will stay where you put it and the problem will disappear.

Service pressures on the Arisaka were absurdly low considering the great strength of the action. About 45,000 was MAX, same as Carcano and .303.

You can make brass easily from .220 Swift, head to the range with a truckload of ammo!
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The picture

brass.jpg
 
Classic low-pressure loads.

Note the one on the LEFT hasn't even flattened the primer: very low pressure.

The middle one grabbed the chamber, the primer backed out a bit and then the case came back and compressed the primer over the firing-pin. Low-pressure loadings.

I note that you have a BIT of headspace. Not a problem; you gotta have SOME. You don't have too much, so don't worry about it. But you CAN get rid of the dimples and such with the pony-tail ties: get the brass expanded to FILL the chamber, then there are NO problems at all. Loads a bit stiffer, with the pony-tail ties, will give you nicely expanded casings which will last a long time.

Good luck.
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HIGHRPM said:
The case body was bulged just above the head, which I think is due to a generous military chamber, and the primers looked like they were showing signs of pressure, flattened and trying to push out ,which I have never had before. I tried two of my lightest loads and both gave the same issue, so I stopped shooting. I have checked everywhere, but it seems no one makes a headspace gauge for this caliber. So, what can I do? Can I try a couple of different bolts, do I try loads that are even lighter than those in the manuals ?
Click to expand...

The bulging in 6.5x50mm Jap cases fired out of Type 38s (and in 7.7mm in Type 99s) is normal. They built the chamber with generous dimensions (similar to Lee Enfields) after their experience in the dirt and grit of China pre-WW2 (hence the dust cover on these fine rifles). The good news I've found is that Norma cases last a long time even with full-length resizing (annealed, though). I haven't thrown one out yet (up to 5 reloadings so far). The bad news is that you won't really be able to neck-size with Arisakas (been there, done that!)

Although it's not hard to find a Type 99 with a matching bolt, I've yet to come across a matching Type 38 (they're out there, but something like hens' teeth!) So if you have the luxury of testing-out many bolts, give it a try. Although my headspace in my Type 38 isn't anything great, I use an IMR 4350 load under a 140gr Nosler (flat bottom, works great with Metford rifling) at around 2200 fps [start at 35.0gr and work up to 38 or so grs] and I find that most of my cases don't need to be trimmed. My reload primers, and the factory Norma primers [~1800fps] are all like yours, flattened, even though the milspec velocity is around 2400fps IIRC, which I've never come near. I've learned to live with it as I've had great results with slower powders in that long bbl.

As a side note, if you're at gun shows looking for brass, try to stick to newer Norma brass since they hadn't perfected the dimensions in their early offerings (60s/70s, I believe).
 
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