Why Now....higher pressures

[Sully2]

Why is it for years we reloaded and stayed at or below about 50K pounds....now Reloads seem to run as high as 64K pounds....why?

And could a person that had been loading ( 270 Win for example) and staying at 50K max poundage create a load that went to say 62,000 pounds for better performance...

 

[CogburnR]

The 270 has been rated at a maximum pressure of 65,000 psi for a very long time.

Max Chamber Pressure - SAAMI Specs

 

[Sully2]

The 270 has been rated at a maximum pressure of 65,000 psi for a very long time.

Max Chamber Pressure - SAAMI Specs

I just used the 270 as an example.....geeze. Try 45-70 then???

 

[gohring3006]

50,000 Copper units of pressure..
65,000 Pounds per square inch..
And I don't believe ther is a equation to convert one to the other...

 

[Sully2]

50,000 Copper units of pressure..
65,000 Pounds per square inch..
And I don't believe ther is a equation to convert one to the other...

Ive never read of any conversion formula at all....??

 

[shaughn]

45-70 has 3 power levels...Mostly....BP load pressure for vintage rifles and replica's...Intermediate for Certain lever actions and near 458 magnum load pressure for Ruger 1 and Siamese Mauser Bolt action to just name a few. Certain rifles both new and old can straddle the lines somewhat, hence the multiple load tables found in some reloading manuals.

The biggest reason is that there was/is a ongoing switch from Copper Units of pressure (CUP) ( which measured how much a copper cylinder was compressed in a special chamber upon firing the test round) to the Piezoelectric force sensor and strain gauges to determine pressure PSI (all have advantages/disadvantages).

There is not a direct translation or equivalent factor between CUP and PSI and I have known many people who have mixed and matched terminology over the years and not just average reloaders and hunters but some brainy people as well.

So with most of the manuals now measuring in PSI versus CUP, the old 50,000 CUP is more likely to be 65,000 +- PSI (random numbers).

Basically what you are seeing is the result of a change in the way they are measuring pressure, not that they are increasing pressure maximums, if anything I believe they are throttling back on some of them because modern testing has revealed that they might be closer to the ragged edge than they believed previously and the modern powders themselves are getting more done with less, which also causes changes.

 

[red dawg]

Thanks for the effort Cogburn!! lol

 

[SansSouci]

Call me a hand loading heretic: I pay very little attention to loading manuals. I used them for reference only.

I used the old school method. I start at an obviously safe load and climb the powder latter until I achieve best velocity or I see indicators of pressure. If it's the latter and accuracy is mediocre, I'll try another powder.

That's why I rely on sources such as Ken Waters' Pet Loads. We don't hunt in laboratories. When hunt where big game is.

 

[243winxb]

There is a competition to have the fastest ammo. Hornady comes to mind.

Brass seems to have pressure limits and how many times the brass can be reloaded at the maximums. Three to five loadings is about it in factory chambers. Primer pockets get larger and leak gas.

Olin had this online a few years ago.

modulus of elasticity- 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. Modulus of Elasticity is 16,000,000 PSI. This means to pull a 1.000 inch long strip to 1.001 inch long induces a 16,000 PSI stress.
So if you pull a 1.000 inch strip to 1.005 inch long, you get about 76,000 PSI, which is the max obtainable.

 

[Mikecr]

Do you agree that it was CUP vs PSI?
Or was there a different context to your question?

 

[Deleted member 46119]

Why is it for years we reloaded and stayed at or below about 50K pounds....now Reloads seem to run as high as 64K pounds....why?

And could a person that had been loading ( 270 Win for example) and staying at 50K max poundage create a load that went to say 62,000 pounds for better performance...

I got a Pressure Trace II for some testing and verification of pressures. It's not laboratory level but it's more accurate than reading primers and brass marks.

I find accurate loads and comfort around 56k or below most of the time. According to everything I read and "reading" my brass across 5 different rifles, 56k is a good point. After that it hurts the brass too fast. On a popular brand action, cases stick above 56k for one of my XX-Nosler wildcats. The same pressure on my Weatherby actions don't stick.

There is a lot to pressures.

 

[shaughn]

It's been awhile since I delved into the subject deeply, but if memory serves for every 5 % increase in velocity there is a 10 % increase in pressure and if new figures are right it's more like 15 %.

 

[J E Custom]

45-70 has 3 power levels...Mostly....BP load pressure for vintage rifles and replica's...Intermediate for Certain lever actions and near 458 magnum load pressure for Ruger 1 and Siamese Mauser Bolt action to just name a few. Certain rifles both new and old can straddle the lines somewhat, hence the multiple load tables found in some reloading manuals.

The biggest reason is that there was/is a ongoing switch from Copper Units of pressure (CUP) ( which measured how much a copper cylinder was compressed in a special chamber upon firing the test round) to the Piezoelectric force sensor and strain gauges to determine pressure PSI (all have advantages/disadvantages).

There is not a direct translation or equivalent factor between CUP and PSI and I have known many people who have mixed and matched terminology over the years and not just average reloaders and hunters but some brainy people as well.

So with most of the manuals now measuring in PSI versus CUP, the old 50,000 CUP is more likely to be 65,000 +- PSI (random numbers).

Basically what you are seeing is the result of a change in the way they are measuring pressure, not that they are increasing pressure maximums, if anything I believe they are throttling back on some of them because modern testing has revealed that they might be closer to the ragged edge than they believed previously and the modern powders themselves are getting more done with less, which also causes changes.

+1
Well said.

Having been around for a long time and loading for 50+ years there have been many changes in loading manuals and firearms so one must figure out what data and philosophy he/she wants to subscribe to.

On the issue of CUPs compared to PSIs there is no direct correlation between the two because of differences in cartridges and chamber dimensions. The main thing is to recognize the strength of
the action and the recommended operating pressure for that action/design.

Older firearms, were not rated as high as new firearms for many reasons and 48,000 to 55,000
Psi (Or its equivalent) should be used in these firearms. Newer firearms are designed for the higher pressures to enhance the velocities (It seems that Everyone wants speed these days) but as discussed, may not be in the best interest of the firearm or the brass cases.

A long time ago I set "MY" max pressure at 62,000 PSIs in modern designed firearms and cartridges and have not regretted it. The rule I use for more velocity is More barrel length, larger case capacity and slower powder burn rates = More velocity @ lower pressure.

Just My Opinion

J E CUSTOM

 

[Deleted member 46119]

...

A long time ago I set "MY" max pressure at 62,000 PSIs in modern designed firearms and cartridges and have not regretted it. The rule I use for more velocity is More barrel length, larger case capacity and slower powder burn rates = More velocity @ lower pressure.

Just My Opinion

J E CUSTOM

That is the level I start to get pretty uncomfortable at as well.