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Japanese Militaria at Castle-Thunder.com
An information board for the Collector of Nippon Militaria
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Smokey
Joined: Sep 07 2006
Posts: 60
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 Posted: Tue Dec 30, 2008 4:01 am Post subject: For the Handloaders - WW760 in the 6.5x50mm |
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I've noticed there's practically no data at all for Winchester 760 ball powder for this cartridge. There's nothing that uses 140gr bullets. Does anyone know why  |
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DEFUC
Joined: Aug 17 2004
Posts: 201
Location: UP of michigan
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| Posted: Fri Jan 02, 2009 9:48 am Post subject: |
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| I expect its about 36-44grs of w-760 for the arisaka, thats the loading for the 6.5x55 and the .260 rem (Ive found anything safe for the 6.5 swede is safe for the arisaka ,generally) I made up a batch of 38 gr loads for the 6.5x50 but havent tried them at the range or thru the chrono yet,so cant say where they are performing.Im building ammo as much as possible all winter,probably wont get to fire a round (that counts) till may (assuming I get away then). |
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Smokey
Joined: Sep 07 2006
Posts: 60
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| Posted: Sat Jan 03, 2009 4:33 pm Post subject: |
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| Any concerns about "secondary pressure spike" in the Type-38's 32 inch barrel? |
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DEFUC
Joined: Aug 17 2004
Posts: 201
Location: UP of michigan
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| Posted: Thu Jan 08, 2009 9:20 am Post subject: |
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| Not terribly ,with that load,"light" loads scare the heck out of me,but mid range doesnt so much..of course Im waiting to see whats what,myself before I really suggest the next guy do something, which is why I said..I plan to try that loading..I havent blown myself up ...YET..I use mu chrono as much as possible and really closely examine spent rounds for any signs of distress,as well as function of the rifle,and I run everything that seems good thru at least 3 test guns of various manufacture.there is a difference in pressure between the carbines and the longs,due to having more time to build,you do have a several hundred FPS differnce between the carbines and the longs (roughly 50 fps per inch with a perfect loading ,as I recall (which means either a lot of waste "heat"with the carbines or a under powered load for the rifles,which is why I have differnt loads for each),but I havent had any serious problems,If I see signs of stress I dont push it.I think it was R-19 I had some issues with,didnt show too much on the case, (tho there was some pressure signs), but after 3-4 rounds you couldnt touch the barrel ,I finally did get it right tho,but found it to be a little too "unstable" versus standbys like 3031 (my "safe" powder for my general purpose ammo).I have found that once you leave the "stand-by" base loadings,whats works perfectly in one rifle may be atrocious in the next,while the basic loads seem to perform well in most guns (my tack driving load in my mukden carbine looks like a buckshot pattern thru my early tokyo,and my pet load in my tokyo long T38 doesnt perform for diddly in my friends T-97) . |
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03man
Joined: Jul 30 2005
Posts: 131
Location: Denver, NC
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| Posted: Sun Jan 11, 2009 11:01 pm Post subject: |
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Well!
It sounds like you need to deveope a nice safe, accurate load.
Work harder!!!!!!!!!!!!!!
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03man |
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Garandshtr
Joined: Dec 27 2007
Posts: 109
Location: Palm Harbor, FL
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| Posted: Thu Feb 12, 2009 8:44 pm Post subject: |
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| Smokey wrote: | | Any concerns about "secondary pressure spike" in the Type-38's 32 inch barrel? |
Since I'm planning on working up a load for my Type 38s, what is a "secondary pressure spike?" Is this a WW760 phenomenon?
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Still trying to learn what I can, mainly about the Type 99 and Type 38. I have more curiosity than time, and more time than money. |
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gwsiii
Joined: Aug 21 2003
Posts: 2229
Location: Hayden, AL
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| Posted: Fri Feb 13, 2009 8:31 am Post subject: secondary pressure |
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Mark, I don't shoot much, I tried to google it, found (what I think is) a good article, related to some commercially available shooting systems (chronographs and such), on barrel harmonics, that explains it, how it happens, some contributing factors, here is an excerpt from it:
| Quote: | from:
http://www.shootingsoftware.com/barrel.htm
http://www.shootingsoftware.com/pressure.htm
The "Catch Up Theory"
...We do not know if the above load suffered from an accelerated burn rate (problematic with some ball powders), but agree with ballistic engineers about the probable cause.
The area under the pressure curve directly relates to the energy imparted to the bullet. The rise to peak pressure engraves the bullet into the rifling and establishes it's initial acceleration down the barrel. The highest rate of acceleration occurs just past the point of maximum pressure. As the bullet travels toward the muzzle, lower pressure coupled with bore friction allows the rate of acceleration (not speed) to fall.
If there is insufficient gas produced by the powder (burn rate too slow), pressure behind the bullet will drop excessively. Then, as the bullet's rate of acceleration falls due to bore friction, gases may "catch up" to the bullet before it exits the barrel and produce a secondary pressure event. In the above load we believe the heat generated from initial ignition coupled with a secondary pressure event increased the burn rate of residual ball powder to near detonation.
Note: Secondary pressures readings taken at the chamber are lower and of longer duration then the actual event due to compression of gasses behind the bullet and the time required for expansion and contraction of barrel steel. The above event may have spanned only .1 milliseconds of time but could have reached 150,000 PSI!
Ball powders do not create the phenomenon of secondary pressures but the resultant pressures can be more severe. Indeed, secondary pressures can even occur when using large extruded powder. When using ball powders it is simply more critical that a powder with the proper burn rate be used to avoid secondary pressures entirely.
In every instance when secondary pressures are detected they can be eliminated by using a faster power, heavier bullet or a bullet with more bore contact area. Normal "tweaking" of loads may change the peak of secondary pressures but will not eliminate the problem. Below is the list of factors we now know can cause secondary pressures.
1. Powder burn rate too slow for the bullet.
2. Bullet weight too light for the powder's burn rate.
3. Bullet bore contact area less then normal for the bullet weight
4. Barrel longer then normal
5. Bore severely worn or incorrectly lapped (loose/worn toward the muzzle)
6. Moly in bore or moly coated bullets that reduce bore friction
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This is part of the Pressure Trace II system.
PressureTrace II ™ is a single channel high speed physical event data acquisition system that captures changes to pressure inside your rifle chamber in real time. It displays a high resolution pressure curve on your computer after each shot so you can compare the total energy delivered by a load, the rise time to peak pressure, affects of bore fouling, seating depth and barrel timing to develop optimum loads or isolate the reasons a load does not work well.
For more related Shooting Software click here.
If anyone has tried any of this, how about a review on pros and cons. Wow, took a little time, and learned something today. I'll be glad to let someone buy me this and I'll have my Dad and his friends test it out now, and have my other shooters test it out in May  Trey
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I didn't pay to much for that old Arisaka, I just bought it a little bit too soon! |
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Garandshtr
Joined: Dec 27 2007
Posts: 109
Location: Palm Harbor, FL
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| Posted: Fri Feb 13, 2009 11:37 am Post subject: don't shoot much? |
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Clearly, not shooting much is a bad thing. At least for me! And, I can get a fix by taking my kids shooting, like I did last Saturday! I must have been somewhat asleep, since I've not heard this term before. I should go and check this out myself, I guess.
thanks,
Mark
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Still trying to learn what I can, mainly about the Type 99 and Type 38. I have more curiosity than time, and more time than money. |
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