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Old December 27, 2012, 09:03 AM   #1
Jevyod
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Pressure question

Forgive me if this is a stupid question but here goes! Is there a good way to check chamber pressure? I have an old K98 8mm Mauser made in 1918 that I would like to work up some loads for. I had it checked out by a gunsmith that knows Mausers like the back of his hand. He told me that although those actions were tested to 75,000lbs pressure, he recommended I keep it somewhere in the neighborhood of 50-55,000. That still enables me to work up some pretty good loads.(much better than the American made factory ammo!) Anyway, how do I know how much pressure my loads are generating? Sorry if this is an amateur question but I still am one! Along with that question, what kind of velocity can I expect to get with a 200 Grn bullet at a 50,000 lb pressure level? Any advice is greatly appreciated!
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Old December 27, 2012, 09:49 AM   #2
243winxb
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QuickLoad -Pressure = estimated

Most reloaders have no pressure testing equipment, so we go by the looks of the brass, primer, web expanding measurement, bolt lift, hard extraction. Some use a chronograph to help get an idea. Compare loading data in manuals & online. http://data.hodgdon.com/main_menu.asp A computer program called QuickLoad,http://www.thehighroad.org/showthread.php?t=685303 may also be helpful to get a reading on pressure. http://www.sniperforums.com/forum/of...-software.html

Last edited by 243winxb; December 27, 2012 at 10:05 AM. Reason: add quickload
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Old December 27, 2012, 01:43 PM   #3
10 Spot Terminator
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All of your top reloading manuals list pressures for starting loads as well as the recommended max loads for a given bullet weight and a specific powder in the calibre you shoot. There are 2 forms of measurement used in the industry , one is PSI and the other CUP depending on the test equipment used during the load testing by the provider of the manuals. There is no formula that I am aware of the convert CUP to PSI at this time but as with PSI if the listings are IN the CUP format, staying with the lower numbers will keep you and your firearm safe.
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Old December 27, 2012, 02:07 PM   #4
Jimro
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You have an M98 action. I wouldn't worry about pressure, just load up for accuracy with an appropriate powder for the bullet you are using and as long as you don't get any of the normal over pressure signs you'll be just fine.

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Old December 27, 2012, 02:24 PM   #5
Bart B.
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Having shot many 7.62 NATO proof loads in Garands that produce 65,000 cup or about 80,000 psi and none showed any signs of pressure on the case or primer, folks claiming one can look for signs of pressure may be leading others astray and into dangerous territory. MIL-SPEC normal max pressure's 50,000 cup or about 60,000 psi. Any data you see will be effected by how hard or soft the brass is in both the primer cup and cartridge case.

My advice is to load 8.57 Mauser no hotter than what decent data suggests. Not all M98 actions have the same strength, so why push the envelope when you don't know how strong it really is? Which is why SAAMI specs for 8x75 ammo's no higher than 37,000 cup or 35,000 psi.
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Old December 27, 2012, 02:49 PM   #6
243winxb
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33 Pressure signs by Unclenick-Link

http://www.shootersforum.com/handloa...ure-signs.html
Quote:
folks claiming one can look for signs of pressure may be leading others astray and into dangerous territory.
Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened.

Last edited by 243winxb; December 27, 2012 at 02:57 PM.
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Old December 27, 2012, 03:47 PM   #7
Unclenick
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If you want to measure pressure, the only system currently in production for handloaders that I am aware of is the RSI Pressure Trace. You can use it in conjunction with QuickLOAD and a chronograph to tweak the QL powder model to match your particular lot of powder better. I use one for three things. One is duplicating load performance. Another is to alert me to the echo of muzzle pressure spikes from using too slow a powder for the bullet weight (see a couple of examples lower down on that page I linked to). A third is that I generally try to stay under 58,000 psi unless I absolutely have to go higher, based on Geoffry Kolbe's observation that barrel erosion tends to grow exponentially with pressure above around that number.
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Old December 27, 2012, 09:55 PM   #8
Jimro
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Bart B.

The 8x57 CIIP pressure standards are a bit higher than SAAMI. The American standards are lower in case some knucklhead get a hold of an old .318 bore 8x57 instead of the .323 bore of the 8x57 JS.

An M98 manufactured in 1918 will have the .323 bore, and if any of the problems of a "weak" action are present, will make itself manifest through lug setback, which is easy enough to check by measuring headspace over time. Loading ammo to a lower pressure won't stop lug setback, just make it slightly slower.

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