Weird Fire Forming Mark Around Shoulder - 6.5 Jap

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HasegawaYamato

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First time doing reloading for the arisaka type 38, found there is weird mark on the fired brass.
I did some research, seems the type 38 serie has the problem of very loose fit between the chamber and the factory brass, which the brass tend to bluge after firing. So is the mark on the shoulder means the shoulder was stretched due to the oversize chamber or I did something wrong with reloading?
Hopefully I can get the pics on :(
Just for info, I used the PPU brass, 140 gr Hornady interlock, and 41 gr of H4895.

Added the link to the pic, since something weird happened and blocked my pic :(
https://photos.app.goo.gl/qSgDthVv3P6m6ziE6

HCtaZg2fiyooqucM9DmVUe2pabAKYFgcXo3TsczA-9lE3PfgwJghUD3uTaepVrgz_1KpDDhKetTrW7osPJIX4rZtB7EWApq9nbmhyA98h0eDTkrodFzFdKVRzzZd9laJjD5SObl3k5gMT8vQSnZm-ekiyJ2mgFdSROLJn7O8xf_ISS4QRQa2dYRnYNCYHD1FsdU2oL4Cf8Wjw7mth51jMatRt5T2mi0z0P-TMGFthbveK0biqYg935BvcxvicmyhWn9tpBqAtv-NqODjZ1GL6F7LQ2eR_IySqPnEaiKBThoMkPnkAhbKjjhZnAg4C1QFCsiGDxCndnwO8TKq-OabGHcLVwIsmuYXp8-3IC4CrNvizBlCeAz_7-tIR-96zAJqXX-sz5tZFIYmm7IMApn07TvBMpPZqECUs6uoPYy1s4bLoGAJEU_uiiV6jdLGAeswO15TJcaYyXo4fs45H2gDNGaqbwhgsg4h0WtNBww-cvUcoMa8RmYCLgu0Ran7MsC8TZqAchvK0X3zwcpieOdjgbtq51iAgi0wirNp8woQlYEko2yNg7srE0SUJO37bsT2QtIz64NwPeJzd8CjSoySiRiYlQhm86Ad0_-NdBWwA9Z0FgMw3t9Ii2Nt7AUs8HrTa7EhO4Aj8rhnsfH4y9qo2wC9hXDKzsJjQ0-J87qe0qlTEJNkP2sybxxNPHm_=w1078-h1263-no
 
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My Lake City 7.62 cases formed to .243 have the same mark on the shoulder. But my guess is chamber reamer marks that show up on your fired brass.

If the rifle does not fail a Field gauge I would say you don't have a problem.
 
Your link works. I have not seen that issue previously - as if your chamber has had some machining that does not quite match with the shape of that re-sized brass? You can be reasonably certain that the fired brass is reflecting the shape of your chamber - that is the whole point of "fire forming" a case. So, compare a fired case to a case that you re-sized - your brass will not last long if your re-sizing process creates a different shaped case than your chamber.

I do not know about your rifle or cartridge, but I have read that WWI Lee Enfield chambers were deliberately reamed larger and deeper than "standard" - this allowed dirty, bent, or other wise damaged and mis-formed cases to be chambered and to be fired. As military rifles, neither the No. 1 Lee Enfield nor yours were meant to be "re-loaded" - the cartridge had to chamber, to fire and to extract, then on to the next cartridge. So you can get longer life out of your fire-formed brass by sizing minimally - just enough that the neck holds a bullet firmly and that the case chambers easily into your chamber. Often this will result in "partial full length sizing" - the sizing die .020" or .030" away from the shell holder - does not matter what gauges or measuring tools say - the brass needs to just so fit into your chamber - which may be a different depth, diameter, etc. than another similar rifle.

If you have a way to inspect inside the chamber, you might see evidence of a second cut? That line I think I see on your fired case's shoulders, also appears where your fired case's shoulder appears to change slope? That is purely a function of the shape of your chamber, so you will not want to alter that when you re-size the cases for your rifle. From the original designers point of view, your re-load has worked fine and the case and the rifle has done its job - it chambered, was fired, and extracted. Trying to re-load the case again, is not something they were concerned about.
 
One further observation - I have no clue how the Japanese did their headspacing design, but the location of that line on your fired brass seems to be very close to where the headspace datum is set for rimless cartridges like the 308 Win or 30-06. They do not "measure" to the point of the shoulder of the case, nor to the junction of shoulder and neck - look at the SAAMI drawings and see there is a "theory" datum diameter established part way along the slope of the shoulder - that is where the headspace measurements are taken from. Pure conjecture on my part - as if the forward portion of your fired case has a second slope, once past that "datum". Might be totally normal - remember they did not care one bit about re-using the brass - it had to work once, then was discarded.
 
Potashminer said:
I do not know about your rifle or cartridge, but I have read that WWI Lee Enfield chambers were deliberately reamed larger and deeper than "standard" - this allowed dirty, bent, or other wise damaged and mis-formed cases to be chambered and to be fired. As military rifles, neither the No. 1 Lee Enfield nor yours were meant to be "re-loaded" - the cartridge had to chamber, to fire and to extract, then on to the next cartridge. So you can get longer life out of your fire-formed brass by sizing minimally - just enough that the neck holds a bullet firmly and that the case chambers easily into your chamber. Often this will result in "partial full length sizing" - the sizing die .020" or .030" away from the shell holder - does not matter what gauges or measuring tools say - the brass needs to just so fit into your chamber - which may be a different depth, diameter, etc. than another similar rifle.
Click to expand...

Thanks for the info. Sadly I dont have tools to check the chamber, so I think the only thing I can do is assume the chamber was imprecisely cutted... From my online research, the arisaka 38 has the larger chamber problem as well, and the case body tends to bulge unevenly. So I think neck sizing only is the best way to go.

I saw someone else saying neck sizing the 6.5 jap can be done by using 6.5 mauser or 6.5 creedmoor FL die, which the body section was larger than the 6.5 jap. I guess I will have to do it this way then. :(
 
Neck sizing only will likely work, but often each time a case is fired, it "springs back" a little less from the chamber, so at some point the shoulder will be a bit too far forward and/or the body will be a bit too fat to slickly chamber - will require a bit of force to close the bolt - at that point, you need to re-size both the body and the shoulder, slightly. At the same time, you will also want to be measuring and dealing with your cartridge case length - there is a maximum length beyond which you must trim those cases - they will grow longer each time it is fired and/or each time it is re-sized. If I were you, I would be buying / using full length dies for that cartridge - look up partial full length sizing - going to leave the last .020" or so of the neck not sized - then when you need to, can turn in that die a half turn more and bump back the shoulder. I am assuming that your chamber is concentric - I have heard of curved chambers that result in "banana" shaped cases - they only go back in one exact orientation, or have to be fully full length sized each time.

You have a milsurp barrel and chamber, not a finely made precision bench rest rig, so don't get too lost in all the very high end reloading detail stuff that the bench rest guys worry about. Your barrel and chamber are not in that league. You want to chamber easily, have your cases short enough not to run into that mouth in the chamber, and pretty much stay with "book" loads and loaded dimensions.
 
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I don't think it's anything wrong with your reloading. The brass is the reverse image of the chamber that fired it and I think what you're seeing is the result of wartime manufacturing and machining.

For the best brass life, use mild-ish loads and resize as minimally as you can. If you can make neck sizing work that would be best.
 
Potashminer said:
Neck sizing only will likely work, but often each time a case is fired, it "springs back" a little less from the chamber, so at some point the shoulder will be a bit too far forward and/or the body will be a bit too fat to slickly chamber - will require a bit of force to close the bolt - at that point, you need to re-size both the body and the shoulder, slightly. At the same time, you will also want to be measuring and dealing with your cartridge case length - there is a maximum length beyond which you must trim those cases - they will grow longer each time it is fired and/or each time it is re-sized. If I were you, I would be buying / using full length dies for that cartridge - look up partial full length sizing - going to leave the last .020" or so of the neck not sized - then when you need to, can turn in that die a half turn more and bump back the shoulder. I am assuming that your chamber is concentric - I have heard of curved chambers that result in "banana" shaped cases - they only go back in one exact orientation, or have to be fully full length sized each time.

You have a milsurp barrel and chamber, not a finely made precision bench rest rig, so don't get too lost in all the very high end reloading detail stuff that the bench rest guys worry about. Your barrel and chamber are not in that league. You want to chamber easily, have your cases short enough not to run into that mouth in the chamber, and pretty much stay with "book" loads and loaded dimensions.
Click to expand...

Really appreciate the help :)

I think I will do neck sizing first then partial sizing after few shots. Now the problem is to find a 6.5 neck sizing die... :(
 
jethunter said:
I don't think it's anything wrong with your reloading. The brass is the reverse image of the chamber that fired it and I think what you're seeing is the result of wartime manufacturing and machining.

For the best brass life, use mild-ish loads and resize as minimally as you can. If you can make neck sizing work that would be best.
Click to expand...

Perhaps do some manual annealing with torch gun after few shots will be even better?
 
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