pressure and velocity - Page 2

Brian Pfleuger · November 20, 2013, 07:15 PM

CUP is the old measuring standard, PSI is newer. Data listed in CUP is simply old data that has not been retested.

MarkCO · November 20, 2013, 08:42 PM

Brian, not so much as standard, but a method. CUP refers to a method of measuring the crush of a calibrated copper pellet by a piston and then that can be compared to known static pressure that causes the same deformation. There is also LUP (lead pellet for lower pressure rounds). The conversion is not direct as there are spikes that the CUP and LUP do not detect. The cost to go back and run all of the cartridges is just not worth it to the bullet and powder manufacturers. The use of modern piezoelectric did not come about until the late 60s for regular pressure testing.

SL1 · November 21, 2013, 09:51 AM

Jerry,

Hodgdon prints data from many sources and many eras. When they acquired Winchester and Alliant powder distribution rights, they often just took the data already developed for those powders in cartridges available at the time. But, there are always new cartridges, so some testing needs to be done for new manuals. And, some old cartridges will also be retested as time and funds permit, especially if powders have been refromulated. But, some old cartridges are so out-of-favor that it is not worth the time and money to reshoot pressure data, so they just keep printing the same old data until they drop that cartridge from the manual to make room for newer cartridges. So, it is not just the "CUP" and "psi" data that are not comparable. Different sources of CUP and different sources of psi data may make those data "apples and oranges" even within the same units.

SL1

Bart B. · November 21, 2013, 09:56 AM

Looked into Quickload's information and noticed the bore cross sectional area for the .224" groove diameter .22-.250 AI barrel example to be .03889 sqare inches. SAAMI's number for the .22-.250 is .03880 square inches based on specific bore, groove and rifling land widths and groove numbers. If those change, so will the bore's cross sectional area and peak pressure for a given load.

I've talked with long range competitors from Great Britain and their comments about shooting 7.62 NATO ammo in their barrels with .2980" bore, .3065" groove and wide lands. Such "tight" bores have much higher pressures than the same ammo shot in NATO spec barrels produce.

I think it would be nice (and more accurate) if Quickload had such dimensions entered into the database to calculate pressure and muzzle velocity from.

Brian Pfleuger · November 21, 2013, 10:04 AM

The effect could possibly be compensated for by using long barrel friction and start pressure adjustments?

F. Guffey · November 21, 2013, 10:39 AM

“I've talked with long range competitors from Great Britian and their comments about shooting 7.62 NATO ammo in their barrels with .2980" bore, .3065" groove and wide lands. Such "tight" bores have much higher pressures than the same ammo shot in NATO spec barrels produce.

I think it would be nice (and more accurate) if Quickload had such dimensions entered into the database to calculate pressure and muzzle velocity from”

I talked to a shooter in Arkansas, I understand talking to someone in Britian? (Britain) is more impressive than talking to a shooter in Arkansas but the results are the same, he was not happy with the low pressure shooting Savage he purchases, his purchased was influenced by all the hype on the Internet about ‘The Savage’. He was using ammo he developed in another rifle, to reduce signs of high pressure he reduced the powder charge by 2 grains. When developing loads for the savage he added 4 grains without showing signs of pressure. He expected better from Savage, he no longer owns the Savage.

Two standards, one for the long range shooters you talk to and another standard for the shooters I talk to.

F. Guffey

Bart B. · November 21, 2013, 10:49 AM

Mr. Guffey, those folks in Great Britain had to use arsenal ammo in their long range fullbore match rifles. They are not allowed to handload nor reload their ammo. That rule was established decades ago based on the premise that if everyone uses the same ammo in a match, then the "playing field" would be leveled and the best marksman would then be decided by scores fired with it.

When arsenal 7.62 NATO bullet diameters are down in the .3070" range, their barrels need .2980" bore and .3065" groove diameters to shoot them accurately. So they get their barrels made to shoot the bullet and ammo they have to use the best possible. And good lots of that arsenal ammo shoots 1 MOA at long range in such barrels; near 1/2 MOA at short ranges where they also shoot.

The two standards you mention are realistically what ammo's allowed, not who one talks to.

jmr40 · November 21, 2013, 07:25 PM

Measuring velocity is the most accurate way to predict pressure for most handloaders. By the time traditional signs show up you are well over where you should be. Every gun is different. For example according to Alliants data 66 gr of Reloder 17 is supposed to be a max load for my 300WSM with 180 gr bullets @ 3082 fps. Working up the load I hit right at 3050 fps with only 64.5 gr in my rifle. Going all the way to 66 gr would have most likely given me quite a bit over 3100 fps and would have been over the max pressure. And likely would have shown no traditional signs of being over pressure. Because I was using a Chronograph I was able to know I was already at a max load in my rifle while still a fair amount below published max powder capacity.

With most of my rifles and powder combo's I find the velocity I get with my rifles matches very close to what the manuals say I should be getting. But at times I've run across individual rifles that are shooting a fair bit slower than the manuals say they should be with that powder/bullet combo. It is PROBABLY safe to add a little more powder until you reach the published speeds IN THAT RIFLE. I would never suggest going over published powder capacity even in this case because of the possibility of that ammo being used in another rifle where it is not a safe load.

steve4102 · November 21, 2013, 08:36 PM

Quote:

Originally Posted by jmr40

By the time traditional signs show up you are well over where you should be.

With that in mind, how far over is "well" over and at at what pressure do these "Traditional" signs show up?

Bart B. · November 21, 2013, 08:47 PM

What pressures do these "Traditional" signs show up?

Most cartridge brass starts to extrude at around 65,000 to 70,000 CUP (80,000+ PSI?) So, if the reverse print of any cutout or hole in the bolt face shows up on a fired case head, that's a "traditional sign" that pressure's too high for what's been deemed safe by metalurgy experts.

std7mag · November 22, 2013, 11:17 PM

Ok, so getting a chrono is fairly cheap, and easy to use..

How does an average Joe like me, making $12 an hour with mortgage and kid, find a way to pressure test his loads???

Brian Pfleuger · November 22, 2013, 11:31 PM

You don't, unless you want to spend $550+ on RSI Pressure Trace.

Jerry45 · November 23, 2013, 01:10 AM

Thanks Brian.

Peter M. Eick · November 23, 2013, 08:17 AM

Brian,

Would you be willing to do a write up on the RSI unit? I would be curious your thoughts and observations in using it.

I have thought about buying one several times but have not followed through. I was thinking of mounting it on my contender which is why I bought it in the first place.

Brian Pfleuger · November 23, 2013, 09:04 AM

Here is the thread about my first experiences. I haven't had time to do much else with it.

I can say that gauge installation is tricky and also extremely critical, not a great combination. I believe it would be best done with a long setting epoxy and a clamp, using a piece of wood fit to the barrel shape.

Clark · November 23, 2013, 09:32 AM

One of my problems has always been, "How do you measure the accuracy of where the strain gauge got glued?"

If you don't know the accuracy of your measurement, you don't get measurements with absolute meaning.

Relative meaning, sure.

A bigger problem is Roark's equations.
No barrel taper, threads, and chamber will ever fit any of those complicated equations for open ended tube stress vs strain.

So again.... relative meaning only.

What does it all mean?
The strain gauge will never compete with knowing the threshold of loose primer pockets.
And for me, never compete with Quickload, which accurately predicts the threshold of loose primer pockets.

Bart B. · November 23, 2013, 09:39 AM

While most of this thread's subject item has been rifles, handguns have an interesting thing on pressure.

SAAMI standard test barrels for revolver cartridges typically list two barrel lengths. One a foot or more long and the other a short, four or so inches with a "vented" barrel setup to emulate the gap between cylinder and barrel. Pressure's measured with the long barrel. Note muzzle velocities from vented short barrels are a few hundred fps less than the longer pressure test ones.

http://www.saami.org/specifications_...wnload/205.pdf

Has anyone measured pressure on revolver cylinders?

Clark · November 23, 2013, 11:31 PM

John Berkovitz explains how the threshold of sticky cases in a 357 mag is the driver for the registered pressure:

https://groups.google.com/forum/?hl=...0/cBSU4bR2jz8J

While he uses math and sticky cases, I am using ultimate strength.

Peter M. Eick · November 25, 2013, 10:46 AM

Clark,

First off I am glad you blew up Colts over S&W's (which I collect).

Your referenced article and a few others you have referenced I think are key to the whole pressure downgrade we have seen in the industry the last 40 odd years.

As a big 357 Magnum fan and shooter, I have been discouraged at the "wimping out" of the 357 Magnum for those of us that like the big N frames and 357 Redhawks.

The specific point that due to the cylinder expansion causing stuck brass in K frame and L frame 357's but not in the N's was an eye opening insight when I first read it. I remember the first time I came across that posting back around 95 or so. It was one of those epiphany moments that you just say "Oh, I am an idiot for not thinking of that myself".

The funny thing is I occasionally forget at put a cylinder of N frame loads in my Pythons. They take it fine, but getting the brass out is usually work. In the big N frames, a light tap on the ejector rod and they all fall out.

SL1 · November 26, 2013, 11:16 AM

Bart, to answer your question, I do remember reading about Speer machining a replacement cylinder for a revolver that preserved the original cylinder's chamber and wall dimensions, including the gap to the barrel, then testing pressues with electronic apparatus that replacement was designed to accomodate. Can't recall right now where I read it. But, I recall the take-away lesson, which was that the pressure trace in the revolver was MUCH different than the trace in the test barrel/universal receiver with the same electronics. Revolver peak was higher and later with full power loads.

SL1

Brian Pfleuger · November 26, 2013, 11:30 AM

It would be interesting to use Pressure Trace on a revolver. There'd certainly be a fudge factor involved, besides the complication of the cylinder not being able to spin. You'd also probably need a gun with a smooth cylinder.

Bezoar · November 26, 2013, 12:27 PM

to create the chamber aspect of the revolver, the initial design would be extremely easy. however fine tuning the gap would be a pain.

November 20, 2013, 07:15 PM	#26
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	CUP is the old measuring standard, PSI is newer. Data listed in CUP is simply old data that has not been retested. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

November 20, 2013, 08:42 PM	#27
MarkCO Senior Member Join Date: October 21, 1998 Location: Colorado, USA Posts: 4,307	Brian, not so much as standard, but a method. CUP refers to a method of measuring the crush of a calibrated copper pellet by a piston and then that can be compared to known static pressure that causes the same deformation. There is also LUP (lead pellet for lower pressure rounds). The conversion is not direct as there are spikes that the CUP and LUP do not detect. The cost to go back and run all of the cartridges is just not worth it to the bullet and powder manufacturers. The use of modern piezoelectric did not come about until the late 60s for regular pressure testing. __________________ Good Shooting, MarkCO www.CarbonArms.us

November 21, 2013, 09:56 AM	#29
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Looked into Quickload's information and noticed the bore cross sectional area for the .224" groove diameter .22-.250 AI barrel example to be .03889 sqare inches. SAAMI's number for the .22-.250 is .03880 square inches based on specific bore, groove and rifling land widths and groove numbers. If those change, so will the bore's cross sectional area and peak pressure for a given load. I've talked with long range competitors from Great Britain and their comments about shooting 7.62 NATO ammo in their barrels with .2980" bore, .3065" groove and wide lands. Such "tight" bores have much higher pressures than the same ammo shot in NATO spec barrels produce. I think it would be nice (and more accurate) if Quickload had such dimensions entered into the database to calculate pressure and muzzle velocity from. Last edited by Bart B.; November 21, 2013 at 11:00 AM.

November 21, 2013, 10:04 AM	#30
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	The effect could possibly be compensated for by using long barrel friction and start pressure adjustments? __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

November 21, 2013, 10:49 AM	#32
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Mr. Guffey, those folks in Great Britain had to use arsenal ammo in their long range fullbore match rifles. They are not allowed to handload nor reload their ammo. That rule was established decades ago based on the premise that if everyone uses the same ammo in a match, then the "playing field" would be leveled and the best marksman would then be decided by scores fired with it. When arsenal 7.62 NATO bullet diameters are down in the .3070" range, their barrels need .2980" bore and .3065" groove diameters to shoot them accurately. So they get their barrels made to shoot the bullet and ammo they have to use the best possible. And good lots of that arsenal ammo shoots 1 MOA at long range in such barrels; near 1/2 MOA at short ranges where they also shoot. The two standards you mention are realistically what ammo's allowed, not who one talks to. Last edited by Bart B.; November 21, 2013 at 01:52 PM.

November 21, 2013, 09:51 AM	#28
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Jerry, Hodgdon prints data from many sources and many eras. When they acquired Winchester and Alliant powder distribution rights, they often just took the data already developed for those powders in cartridges available at the time. But, there are always new cartridges, so some testing needs to be done for new manuals. And, some old cartridges will also be retested as time and funds permit, especially if powders have been refromulated. But, some old cartridges are so out-of-favor that it is not worth the time and money to reshoot pressure data, so they just keep printing the same old data until they drop that cartridge from the manual to make room for newer cartridges. So, it is not just the "CUP" and "psi" data that are not comparable. Different sources of CUP and different sources of psi data may make those data "apples and oranges" even within the same units. SL1

November 21, 2013, 10:39 AM	#31
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	“I've talked with long range competitors from Great Britian and their comments about shooting 7.62 NATO ammo in their barrels with .2980" bore, .3065" groove and wide lands. Such "tight" bores have much higher pressures than the same ammo shot in NATO spec barrels produce. I think it would be nice (and more accurate) if Quickload had such dimensions entered into the database to calculate pressure and muzzle velocity from” I talked to a shooter in Arkansas, I understand talking to someone in Britian? (Britain) is more impressive than talking to a shooter in Arkansas but the results are the same, he was not happy with the low pressure shooting Savage he purchases, his purchased was influenced by all the hype on the Internet about ‘The Savage’. He was using ammo he developed in another rifle, to reduce signs of high pressure he reduced the powder charge by 2 grains. When developing loads for the savage he added 4 grains without showing signs of pressure. He expected better from Savage, he no longer owns the Savage. Two standards, one for the long range shooters you talk to and another standard for the shooters I talk to. F. Guffey

November 21, 2013, 07:25 PM	#33
jmr40 Senior Member Join Date: June 15, 2008 Location: Georgia Posts: 10,806	Measuring velocity is the most accurate way to predict pressure for most handloaders. By the time traditional signs show up you are well over where you should be. Every gun is different. For example according to Alliants data 66 gr of Reloder 17 is supposed to be a max load for my 300WSM with 180 gr bullets @ 3082 fps. Working up the load I hit right at 3050 fps with only 64.5 gr in my rifle. Going all the way to 66 gr would have most likely given me quite a bit over 3100 fps and would have been over the max pressure. And likely would have shown no traditional signs of being over pressure. Because I was using a Chronograph I was able to know I was already at a max load in my rifle while still a fair amount below published max powder capacity. With most of my rifles and powder combo's I find the velocity I get with my rifles matches very close to what the manuals say I should be getting. But at times I've run across individual rifles that are shooting a fair bit slower than the manuals say they should be with that powder/bullet combo. It is PROBABLY safe to add a little more powder until you reach the published speeds IN THAT RIFLE. I would never suggest going over published powder capacity even in this case because of the possibility of that ammo being used in another rifle where it is not a safe load.

November 21, 2013, 08:47 PM	#35
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	What pressures do these "Traditional" signs show up? Most cartridge brass starts to extrude at around 65,000 to 70,000 CUP (80,000+ PSI?) So, if the reverse print of any cutout or hole in the bolt face shows up on a fired case head, that's a "traditional sign" that pressure's too high for what's been deemed safe by metalurgy experts. Last edited by Bart B.; November 21, 2013 at 09:02 PM.

November 22, 2013, 11:17 PM	#36
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	Ok, so getting a chrono is fairly cheap, and easy to use.. How does an average Joe like me, making $12 an hour with mortgage and kid, find a way to pressure test his loads???

November 22, 2013, 11:31 PM	#37
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	pressure and velocity You don't, unless you want to spend $550+ on RSI Pressure Trace.

November 23, 2013, 01:10 AM	#38
Jerry45 Senior Member Join Date: April 18, 2000 Location: Metairie, Louisiana Posts: 890	Thanks Brian. __________________ Guns are not dangerous! People are! RKBA!

November 23, 2013, 08:17 AM	#39
Peter M. Eick Senior Member Join Date: August 3, 1999 Location: Houston, Texas Posts: 2,991	Brian, Would you be willing to do a write up on the RSI unit? I would be curious your thoughts and observations in using it. I have thought about buying one several times but have not followed through. I was thinking of mounting it on my contender which is why I bought it in the first place. __________________ 10mm and 357sig, the best things to come along since the 38 super!

November 23, 2013, 09:04 AM	#40
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	Here is the thread about my first experiences. I haven't had time to do much else with it. I can say that gauge installation is tricky and also extremely critical, not a great combination. I believe it would be best done with a long setting epoxy and a clamp, using a piece of wood fit to the barrel shape. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

November 23, 2013, 09:32 AM	#41
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	One of my problems has always been, "How do you measure the accuracy of where the strain gauge got glued?" If you don't know the accuracy of your measurement, you don't get measurements with absolute meaning. Relative meaning, sure. A bigger problem is Roark's equations. No barrel taper, threads, and chamber will ever fit any of those complicated equations for open ended tube stress vs strain. So again.... relative meaning only. What does it all mean? The strain gauge will never compete with knowing the threshold of loose primer pockets. And for me, never compete with Quickload, which accurately predicts the threshold of loose primer pockets. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?

November 23, 2013, 09:39 AM	#42
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	While most of this thread's subject item has been rifles, handguns have an interesting thing on pressure. SAAMI standard test barrels for revolver cartridges typically list two barrel lengths. One a foot or more long and the other a short, four or so inches with a "vented" barrel setup to emulate the gap between cylinder and barrel. Pressure's measured with the long barrel. Note muzzle velocities from vented short barrels are a few hundred fps less than the longer pressure test ones. http://www.saami.org/specifications_...wnload/205.pdf Has anyone measured pressure on revolver cylinders?

November 25, 2013, 10:46 AM	#44
Peter M. Eick Senior Member Join Date: August 3, 1999 Location: Houston, Texas Posts: 2,991	Clark, First off I am glad you blew up Colts over S&W's (which I collect). Your referenced article and a few others you have referenced I think are key to the whole pressure downgrade we have seen in the industry the last 40 odd years. As a big 357 Magnum fan and shooter, I have been discouraged at the "wimping out" of the 357 Magnum for those of us that like the big N frames and 357 Redhawks. The specific point that due to the cylinder expansion causing stuck brass in K frame and L frame 357's but not in the N's was an eye opening insight when I first read it. I remember the first time I came across that posting back around 95 or so. It was one of those epiphany moments that you just say "Oh, I am an idiot for not thinking of that myself". The funny thing is I occasionally forget at put a cylinder of N frame loads in my Pythons. They take it fine, but getting the brass out is usually work. In the big N frames, a light tap on the ejector rod and they all fall out. __________________ 10mm and 357sig, the best things to come along since the 38 super!

November 26, 2013, 11:16 AM	#45
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Bart, to answer your question, I do remember reading about Speer machining a replacement cylinder for a revolver that preserved the original cylinder's chamber and wall dimensions, including the gap to the barrel, then testing pressues with electronic apparatus that replacement was designed to accomodate. Can't recall right now where I read it. But, I recall the take-away lesson, which was that the pressure trace in the revolver was MUCH different than the trace in the test barrel/universal receiver with the same electronics. Revolver peak was higher and later with full power loads. SL1

November 26, 2013, 11:30 AM	#46
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	It would be interesting to use Pressure Trace on a revolver. There'd certainly be a fudge factor involved, besides the complication of the cylinder not being able to spin. You'd also probably need a gun with a smooth cylinder. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

November 26, 2013, 12:27 PM	#47
Bezoar Junior member Join Date: October 19, 2004 Location: michigan Posts: 578	to create the chamber aspect of the revolver, the initial design would be extremely easy. however fine tuning the gap would be a pain.