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Discussion Starter #1 (Edited)
Pressure Test Rifle





Topic author: Edokko
Subject: Pressure Test Rifle
Posted on: 10/14/2006 12:48:05 AM
Message:

Don't know how many of you board members own a pressure test rifle or examined one up close, but here are photos of an example that has a test chamber type that I have never seen before. Usual test chamber has a thumb screw cover that keeps the crusher disc in place, but this one has a totally different assembly with a thread on the top end where some kind of device or sensor must have been screwed on. The piece with the round side windows on both sides is a mystery as to it's mechanism since it refuse to disassemble.

The receiver is based on the T-38, the chamber is designed for the 7.7mm cartridge, and the dust cover size is that of a T-99 length. Also notice the floor plate is hinged like a T-99. There are no arsenal marks on the rifle but the Kokura "se" inspection mark and the serial # 22 stamped on some of the parts.

Have anyone seen such example of this variation before and does anybody out there know how this pressure testing mechanism work ?? Any info would be appreciated.


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Replies:

Reply author: rblue
Replied on: 10/14/2006 08:55:55 AM
Message:
When you said it was nice you weren't kidding!!!!
Great find.
R.B.

Reply author: Jareth
Replied on: 10/14/2006 09:46:13 AM
Message:
I have near identical pressure test rifle. Mine is also a type 38/type 99 mix. It's in 7.7. as well. Probally used to test new caliber 7.7 when introduced early on. I mailed test device that screws into top of pressure chamber to ADogs & he photographed it in disembled & in detail & posted it here. It was a finely made, high blued metal cylinder with two cut out windows, a few (3?) light alloy discs fit/slid in then had a threaded screw cap with a pressure set turn knob on top. Had to be a year ago. I'd need better photos from you but it looks incomplete( device not rifle) compared to mine. Interesting I've never seen a dust cover on a pressure test rifle. Is it numbered/matching? Maybe you can do a search or Rob might have an idea how to bring up that old post.

Reply author: Edokko
Replied on: 10/14/2006 11:00:35 AM
Message:
Roscoe, hehe thanks ! The Jag show was pretty good on me.
Jareth, that's great info ! I will attach close-ups of the device per below, but right now I did manage to dissasemble it using a plastic mallet, and it does seem to be missing the top lid cover to hold the contents inside under pressure. It would be great to see photographs of your device, to see what the lid looks like (Rob, can you pull one out of your hat ?). This should be a tough one but I will have to go on a quest for the missing part !
Yes, the dust cover is unusual, but I guess the cover may also effect the pressure build-up (although infinitely minor) and the designers may have kept them on. The cover does not have any serial or assembly number but has the Kokura "se" inspection mark on the lip. It also has the "L" shaped strut that makes it probably one of the first ever T-99 cover variations !

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Reply author: Jareth
Replied on: 10/14/2006 11:25:57 AM
Message:
Yes, device is extremely similar to mine! Are the discs still present? I can't tell from your photos. Unfortunately your screw cap is missing. If you can't bring up old post through a search then lets hope Rob will help out. Regarding dust cover, I have matching 99 long that has matching dust cover with "L" bracket as well as a hybrid sling that's as long as a type 38 sling but wide like 99 sling with typical type 99 buckle.

Reply author: arisakadogs
Replied on: 10/14/2006 12:57:46 PM
Message:
Here's some photos I took of camera shy Jareth's test device. I shot some of these along side the PT rifle I used to have. Note the different thread where they screw into the rifle. These were not interchangable.

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The large cylinder is solid & the smaller one comes apart & has these springs in it. Wonder how they were used?
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Reply author: Edokko
Replied on: 10/14/2006 1:13:01 PM
Message:
Rob, thanks !!
I may be missing another piece, the cover for the spring casing. Boy this is going to be a long search for these parts ! Goign to keep my fingers crossed in finding one in Tulsa....
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I'm not sure where the discs are placed, but if it was placed between the two cylinders peeking through the side windows, the discs are gone but only a strange looking tension spring that radiates out to the circumference.

Jareth, what is the serial # and length of your barrel ? Mine is #22 and the barrel from end of chamber to muzzle is 72.5cm.

Reply author: arisakadogs
Replied on: 10/14/2006 1:39:29 PM
Message:
You are most welcome Edokko. Too bad you're missing some parts. I think finding them will be nothing short of a miracle! The number 3 appears on Jareth's spring disc.

Reply author: Jareth
Replied on: 10/14/2006 5:15:20 PM
Message:
I'll get you barrel length tomorrow night. As Rob said I believe my rifle is serial #3. Rob, thanks for photographing my "device" & reposting it & now you don't need to see my rifle as it's identical to Edokko's post! I'm excited another one of these has turned up!

Reply author: Clyde from Carolina
Replied on: 10/15/2006 08:47:55 AM
Message:
Fascinating pieces. They appear to be high quality jobs. Edokko, good luck on finding the missing bits for your rifle.

Reply author: Edokko
Replied on: 10/15/2006 11:21:49 AM
Message:
Thanks Clyde, I need as much luck as I can muster on this one. I have started with asking the person who sold me this rifle to check the original owner for any extra pieces laying around his house. Fingers crossed !!
But, even without the missing pieces, this pressure test rifle is as you say a really fascinating piece, extremely nice condition too, and can't help but ogle at it all day long !

Reply author: Jareth
Replied on: 10/15/2006 10:48:43 PM
Message:
Edokko my rifle is serial #3. Barrel length is 28 1/2"

Reply author: arisakadogs
Replied on: 10/15/2006 10:56:11 PM
Message:
At one time I thought about selling every thing else & only persuing PT rifles. Thank God I sobered up! Can you imagine how frustrating it would be to know about a varient you need & not be able to obtain it?? So rare, yet still under appreciated.

Reply author: Edokko
Replied on: 10/15/2006 11:02:38 PM
Message:
Jareth, thanks, that means we have identical pressure test rifles, interesting. Does your have any difference in finish on the muzzle end ? looks as though something was fitted over the end.

Reply author: Jareth
Replied on: 10/15/2006 11:35:29 PM
Message:
I can't recall but I'll recheck condition on my muzzle end. I agree with Rob, these pressure test are THE rarest rifles! Let me know if you ever figure out how "device" was used in testing.

Reply author: JLKwilinski
Replied on: 10/17/2006 4:28:37 PM
Message:
Hay Edokko,
Your PT looks to me as a transition piece from T38 style to T99 style. You didn't state what the barrel length on yours was or the over all length. Has it got any numbers stamped on it? The pressure chamber on your PT is one I haven't seen before. I'm not even sure how it is supposed to work.
The T99 PT I have is from the Kokura arsenal and is serialed #16. It is stamped on the receiver, barrel and on the tapered part of the bolster. It is also stamped with the (u)= 24 symbol on the bolster. The bolt, pin, extractor, safety and dust cover arn't numbered. Mine is chambered for the 7.7 Rimless rifle cartridge. The barrel on mine can be unscrewed after removing a pin in the front screw hole of the trigger guard.
JLKwilinski


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Reply author: Edokko
Replied on: 10/17/2006 6:58:07 PM
Message:
JLK, nice piece you got there. Your's is the second only PT rifle I've seen that comes with an intact dust cover. The Kanji "u" followed by 12 on your stock may mean something, one guess is the "u" may come from the location Ujina (same initial Kanji) in Hiroshima and could have been the direct supervising arsenal for Toyo Kogyo (present Mazda) for the new T-99 rifles to be produced there, just a guess though.

My example, the 7.7mm rimless PT rifle on a T-38 base, is serialed #22 on various parts and an assy #12 on the trigger guard and the extractor. The length of the barrel is 72.5 cm or 28.5 inch, and seems to be exactly the same as Jareth's.



Reply author: JLKwilinski
Replied on: 10/17/2006 7:00:38 PM
Message:
Edokko,
I had to go and check my PT for lengths. The over all length is 49 5/8". The barrel is 31 7/32" muzzle to bolt face and 28 5/16" Muzzle to bolster. The stock is a modified T99 long with no sling swivel mortice. The pill chamber is the three piece type. I looked back at your posting and saw that your PT is #22 (Kokura?)
JLKwilinski

Reply author: Edokko
Replied on: 10/17/2006 7:10:07 PM
Message:
The barrel seems to be the same length then, interesting, perhaps 28.5 inches or 72.5 cm was the standard length of barrels for 7.7mm PT rifles. Yes, my rifle is also made in Kokura, assuming from the "se" proof marks seen on various metal parts of the receiver and bolt assy. However, it is missing the arsenal mark on the receiver side.
I am trying to figure out how the device worked in terms of pressure testing. The testing device is very unusual and does not seem like the "metal disk crusher" type seen on other PTs. The spiral spring in the two piece flat cylinder must be the clue. More research needed.

Reply author: arisakadogs
Replied on: 10/17/2006 10:42:15 PM
Message:
Edokko, have you checked your rifle to see if it's for rimless or semi-rimmed 7.7mm? The one I had was for semi-rimmed. I'd hazard a guess that yours & Jareth's may be for the HMG ammo as well. That's why they used a T-38 action - the T-99 rifles wasn't in production yet.

Reply author: JLKwilinski
Replied on: 10/18/2006 3:49:23 PM
Message:
Edokko,
Just on a hunch I checked MROJ and the picture of the Kokura T99 Long PT in it is like my PT in this post. It is serialed 22. So if yours is #22! What do you think?
JLKwilinski

Reply author: Edokko
Replied on: 10/18/2006 8:27:22 PM
Message:
A-dogs, yes I will defnitely need to check if the action also fits the semi-rimmed 7.7mm. I'll need to dump the powder out of one of my MG 7.7mm ammo just in case it doesn't go off while cycling. An observation I need to point out though, is the T-99 length dust cover, and the hinged magazine floor plate, which both were eventually incorporated into the T-99 design, but not on the T-38, so I think the T-99 was already at least in the design stage when this PT was made.

JLK, I don't know what to think of the #22 connection between mine and MROJ pictured PT rifle, but I'm thinking just a coincidence, since these numbers do seem to be serial #s and not some sort of designation number for the type of the test. By the way, about where in relation to the cartridge / bullet is the pressure testing device (the crusher disk chamber) positioned on your PT ? Mine is positioned right above the cartridge case body itself, and Fred has advised to me that it was used to measure bleed-by pressure in designing the tolerance of the cartridge diameter margin.

Reply author: arisakadogs
Replied on: 10/18/2006 10:31:08 PM
Message:








quote: Originally posted by Edokko
A-dogs, yes I will defnitely need to check if the action also fits the semi-rimmed 7.7mm. I'll need to dump the powder out of one of my MG 7.7mm ammo just in case it doesn't go off while cycling. An observation I need to point out though, is the T-99 length dust cover, and the hinged magazine floor plate, which both were eventually incorporated into the T-99 design, but not on the T-38, so I think the T-99 was already at least in the design stage when this PT was made.
Edokko, you don't need to pull the bullet. Just see if the head of the round will fit on the end of the bolt. You can have the firing pin out to be safe.
I didn't notice the hinged floorplate till you mentioned it. Still a T-38 style latch - interesting. The one I had still has the 6.5mm size magazine so it had to have been loaded single shot.

Reply author: fredh
Replied on: 10/19/2006 4:20:50 PM
Message:
Edokko, I don't know for sure not having examined the bolster assy, but it is "possible" that they were determining the effect of cartridge case/chamber wall clearance on bleed-by. A mil clearance one way or the other can have a terrific effect on bleed-by. Ordnance wanted as large a clearance as possible to account for trash in the action. There is a point where pressure will go asymptotic as the chamber clearance increases. Edokko, when I told you that, I was pulling a John Wayne and shooting from the hip. Sometimes I hit the target.

Reply author: JLKwilinski
Replied on: 10/19/2006 11:25:23 PM
Message:
Edokko,
The pressure chamber is more or less centered over the cartridge case on my T99 PT.

When I have to insert a cartridge into one of my J
apanese rifles, I remove the pin and sometimes the extractor to check the fit of the round in the chamber. You can close the bolt and shove a rod down the barrel and with the rifle muzzle down and holding the rod, you can feel the amount of up and down movement of the cartridge in the chamber. You don't have to empty the powder out of the cartridge. You can just about feel if there is to much play, altho it's not like using headspace gages.

JLKwilinski

Reply author: rcb
Replied on: 11/11/2006 5:21:44 PM
Message:
Here are the parts you needed.Will ship Monday. rcb


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Reply author: Edokko
Replied on: 11/11/2006 7:48:16 PM
Message:
Holy moly mother by golly !!! You just recieved Jareth's original parts just a day before yesterday, and the parts are already finished !!!! You sir are one incredible genius of a machinist. I will not be able to sleep with my feet towards your direction (Japanese saying for full total respect).
The drinks are on me in Phoenix !!

Thank you most deeply.

Reply author: Edokko
Replied on: 11/17/2006 01:41:31 AM
Message:
Laaaadies, and gentlemen ! Behold ! the work of a true genius !!!
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I just stand in awe at the craftsmanship of Roy, and his graciousness to help this poor soul. Also special gratitude to Jareth who has so kindly volunteered to send his precious parts to be the model of Roy's art.

Thank you in the deepest gentlemen, and I am again struck by the greatness of the fraternity of this board. Banzai !!!

Reply author: arisakadogs
Replied on: 11/17/2006 09:25:01 AM
Message:
That is way cool!

Reply author: fredh
Replied on: 11/17/2006 12:48:47 PM
Message:
Edokko, that is one fine looking piece of machinery!

Reply author: Edokko
Replied on: 03/23/2007 8:23:24 PM
Message:
Gentlemen, just wanted to update you on the findings of the pressure testing device on mine and Jareth's PT rifle variation.
A fellow Japanese collector residing in southern California, who also owns the same variation PT rifle serial #20, but which was missing the whole PT device, had obtained information through his website that effectively nailed down the system that the pressure test device worked on. Apparently, a university professor in Japan looked at a photo of my device posted on my fellow collectors' website and contacted him describing this device as being a powder performance testing device based on the "Kast brisance test" method. The "brisance" value is the powder's explosive and pressure characteristics measured through pressure loading density and detonation velocity and other parameters. The Kast test method itself is conducted by compressing copper or lead cylinders through a piston device, and comparing the post compression shape against a known value.
So, for our device, either a small copper or lead (most likely copper) cylinder was placed between the two facing cups, the bottom of the cylinder pinched between the "yingyang" looking spring to stabilize at the center. The cap was placed over the set up with the thumb screw securing everything down. When the cartridge was detonated, the "bleed-by"gas pushes the small piston-ball bearing link up the bottom cup and compresses the copper cylinder up against the upper cup, showing the powder brisance value.
Does this make sense ? Neat huh ?

Reply author: seinen
Replied on: 03/23/2007 8:32:47 PM
Message:

Takehito,

I wonder how tough it would be to make contact with the Japanese professor. I'd like to know if he has, or could gain, access to any original arsenal pressure testing rifle design schematics or other technical information related to these weapons.

C/

Reply author: Edokko
Replied on: 03/23/2007 8:38:15 PM
Message:
Chip, I think that's going to be a toughy. The professor has approched this identification through his academic angle of the study of explosive power, and not necessary related to old Japanese military items.

Reply author: seinen
Replied on: 03/23/2007 9:11:25 PM
Message:

Takehito,

Yes, probably so. However, I thought it might be worth an attempt since the professor would be familiar with more than a few previous studies on the matter, possibly including wartime efforts.

C/

Reply author: Jareth
Replied on: 03/23/2007 11:19:05 PM
Message:
Thanks for the update Takehito.

Reply author: Edokko
Replied on: 03/24/2007 12:37:53 AM
Message:
Chip, yes, perhaps if I can have the collector in LA ask the prof. but could be a far shot. Will try checking out the Archives for this topic too when I'm in Tokyo next.

Jareth, sure thing, couldn't have gone this far without your help in lending me and Roy the parts from your PT rifle. Next thing for me is to somehow find a diagram of the Type 4 knife bayonet.


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