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#3034810 - 01/19/17 04:33 PM Re: Understanding Pressure [Re: orkan]
GhostsoftheGrass Offline
Seasoned Member

Registered: 01/09/13
Posts: 191
Loc: NE
Very good! Thank you, sir!

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#3140369 - 03/20/18 06:07 AM Re: Understanding Pressure [Re: GhostsoftheGrass]
Bauxite Offline
New Member

Registered: 06/17/17
Posts: 4
Loc: The Jungles of Arkansas
Let me say thank you, too. Excellent.
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#3157218 - 08/02/18 12:03 AM Re: Understanding Pressure [Re: orkan]
Wa_Coyote_Hunter Offline
Die Hard Member

Registered: 12/16/06
Posts: 745
Loc: central washington
nice read saved on my computer for future reading. got a 357 mag from my uncle 30 years ago. with some reloads. fired a few rounds then bang pierced a primer. the sound of the shot sounded like it doubled. disposed of the rest of those rounds in a hurry.
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#3174042 - 11/27/18 11:08 PM Re: Understanding Pressure [Re: orkan]
Predzys Offline
New Member

Registered: 11/19/18
Posts: 7
Loc: IL
Nice write up

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#3187905 - 01/23/19 09:14 PM Re: Understanding Pressure [Re: orkan]
Flesh Eater Offline
Die Hard Member

Registered: 03/09/17
Posts: 665
Loc: 2D Pennsylvania
Very good article!

I’m thinking about getting into reloading and this was an eye opener even about factory ammo! Which after reading it I checked some casings on my once fired .17 Hornet brass. Sure enough, the Hornady 25 grain JHP was hot enough to make the primer look like your early pictures of cratering.

My question about the oil is how do you deal with rifles that get ice all over them, then sweat when brought in? Oil seems unavoidable.
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#3187926 - 01/23/19 10:25 PM Re: Understanding Pressure [Re: orkan]
Rock Knocker Online
Die Hard Member III

Registered: 12/29/11
Posts: 3090
Loc: Buffalo, MN
Originally Posted By: Flesh Eater

My question about the oil is how do you deal with rifles that get ice all over them, then sweat when brought in? Oil seems unavoidable.


When I get home from hunting in the cold, -15 to -20 at times. I ether leave the gun in the case until it's all at room temp or I take the gun out, dang thing freezes solid, literally, but field strip the gun as much as I can and place the parts over some of my furnace vents and that warms it up and drys it off pretty quick. Plus not having enough lube for it all to be flowing around helps also.

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#3187997 - 01/24/19 09:23 AM Re: Understanding Pressure [Re: Rock Knocker]
Flesh Eater Offline
Die Hard Member

Registered: 03/09/17
Posts: 665
Loc: 2D Pennsylvania
Originally Posted By: Rock Knocker
Originally Posted By: Flesh Eater

My question about the oil is how do you deal with rifles that get ice all over them, then sweat when brought in? Oil seems unavoidable.


When I get home from hunting in the cold, -15 to -20 at times. I ether leave the gun in the case until it's all at room temp or I take the gun out, dang thing freezes solid, literally, but field strip the gun as much as I can and place the parts over some of my furnace vents and that warms it up and drys it off pretty quick. Plus not having enough lube for it all to be flowing around helps also.


I've noticed my rifles seemingly dry up within an hour, but they sweat like crazy during the process. I assume if it's sweating on the outside of the barrel, it has to be sweating inside, right?

Do you oil your chamber at all? Would oiling it, then wiping it with a dry rag, or dry swab create the same pressure issues as discussed, or is that usually caused by an excess of oil?
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#3211172 - 08/29/19 11:57 PM Re: Understanding Pressure [Re: orkan]
JMette Offline
Junior Member

Registered: 02/05/18
Posts: 45
Loc: illinois
Velocity =‘s pressure. That helps a lot if you know roughly where your rifle should be shooting.
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Jeremy Mette

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#3211173 - 08/30/19 12:00 AM Re: Understanding Pressure [Re: JMette]
orkan Offline
Die Hard Member II

Registered: 06/27/03
Posts: 1745
Loc: Western SD
Originally Posted By: JMette
Velocity =‘s pressure. That helps a lot if you know roughly where your rifle should be shooting.


To clarify, are you saying velocity is an indicator of pressure?

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#3211257 - 08/31/19 12:56 AM Re: Understanding Pressure [Re: orkan]
JMette Offline
Junior Member

Registered: 02/05/18
Posts: 45
Loc: illinois
It could be. It’s the closest thing we have to measuring pressure. Nothing is the same in reloading. Everything is different and has variables. But if a safe pressure in a manual states a given FPS with a certain grain. It may take your rifle 1 grain more powder to achieve them same results or it may take your rifle 1/2 grain less. If you’ve got a loose barrel you won’t have pressures therefore you won’t have the velocities. If you’ve got a tight barrel you’ll have increased pressure and therefore you’ll get an increase in velocity with a lower powder charge

Hope makes sense.
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#3211258 - 08/31/19 01:00 AM Re: Understanding Pressure [Re: orkan]
JMette Offline
Junior Member

Registered: 02/05/18
Posts: 45
Loc: illinois
So essentially, yes velocity = pressure. Higher the pressure the more the velocity. Lower the pressure the lower the velocity. Only thing we’ve got to measure pressure is to judge by book velocity. Primer crater, head swipes, flatten primmer, can all show false pressures. And no signs doesn’t necessarily mean no high pressure either.
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Jeremy Mette

-Shoot Straight... Shoot often-

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#3211275 - 08/31/19 10:48 AM Re: Understanding Pressure [Re: JMette]
Bob_Atl Offline
Die Hard Member III

Registered: 01/09/15
Posts: 2081
Loc: in the field, or not..
An old thread !

Need to be careful on the oversimplification of MUZ-V == PSI.

To illustrate, some powders will give a spike of pressure, above max PSI,
while other powders will give a safe smoothed mound of pressure for same MUZ-V.

A handy tool to see examples of estimated pressure curve shape is Quickload.
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#3211390 - 09/01/19 09:49 PM Re: Understanding Pressure [Re: Bob_Atl]
JMette Offline
Junior Member

Registered: 02/05/18
Posts: 45
Loc: illinois
I use quickload frequently. It’s a broad analysis about velocity but it’s true mostly to an extent.
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Jeremy Mette

-Shoot Straight... Shoot often-

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#3211503 - 09/03/19 01:13 PM Re: Understanding Pressure [Re: orkan]
orkan Offline
Die Hard Member II

Registered: 06/27/03
Posts: 1745
Loc: Western SD
JMette, I can not agree with your assessments here. Velocity is a result, and while some correlation exists, correlation does not imply or equal causation.

Especially in this case, because as Bob Atl said, pressure is pressure, and is not velocity specific in any instance. This is easily evidenced by the same loads being able to produce 100fps more or 100fps less in different barrels. So while velocity will be a metric for the median, to either side of the median is danger.


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#3213547 - 09/29/19 12:59 PM Re: Understanding Pressure [Re: orkan]
Don Fischer Offline
Seasoned Member

Registered: 12/19/09
Posts: 491
Loc: Antelope, Ore
Every thing you need to now about pressure. To much can blow up any rifle and do a lot of damage to you. Doesn't matter what the pressure is as the overwhelming majority of us have no means to measure it. That mean's pressure is just a number! What is important is to learn to recognize pressure sign's and how to avoid them. Then suddenly the number means nothing anymore because you'll never know what your getting in the first place. What you need to know is how to recognize dangerous pressure when you see it!


Edited by Don Fischer (09/29/19 01:00 PM)

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