SAAMI vs. Hodgdon pressures

Hodgdon publishes pressures along with their reloading data on their website. I'm interested in the .357 Magnum data, and a great many of their maximum loads are higher than the SAAMI max of 35,000 psi. Why would they publish these, and am I at risk of damaging my GP100 by following these published loads?

There are no .357 Mag loads on Hodgdons website higher then 35,000 PSI.
In fact there are no loads even reaching 35,000 PSI.

I think you might be looking at the loads with pressure listed in CUP units.

CUP, or Copper Units of Pressure, is not the same thing as PSI or Pounds Per Sq Inch.
And the two cannot be converted or compared to each other

CUP is the old pressure measuring method used before the new pressure transducer method has been adopted.

Anything they publish is safe in your GP100, assuming you start with the starting load and work your way up to the max while looking for excess pressure signs such as hard extraction, etc.

rc

D'oh, you got me. I didn't notice that they go back and forth between CUP and PSI.

And RC nails it again!
That is in fact the correct explanation, CUP and PSI are not convertable, nor can they be compared with any useful results. I do however wonder why Hogdon is still publishing pressures in CUP? That unit of measuring pressures is basically obsolete since the introduction of PSI units into the reloading world.

I think probably because they don't have enough lab time or personnel to retest thousands of loads that have been proven safe for many many years.

Besides that, Hodgdon keeps coming out with new powders, and other manufactures new calibers, which triggers a whole new round of load development & testing for numerous calibers all over again.

Probably just not enough lab time to up-date old data that doesn't need updating anyway.

rc

Or they may still own a crusher gun.

The main thing is, it doesn't matter.
CUP or piezo psi, maximum is maximum whichever system they report in.

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

The 357 mag was invented by reaming out a 38 special and then working up loads until the cases stuck and then backing off a safety margin so the cases do not stick.
The SAAMI registered pressure for 357 mag was chosen so that cases would not stick when 357 mag factory ammo was put in any production 357 mag revolver.
To do that, they worked up loads until the cases stuck, backed off a safety margin so they would never stick, and then measured the pressure of the reduced loads.
Hodgdon works up loads with pressure measurement, and tries to duplicate that pressure.
Handloaders buy Hodgdon's data or get it free, and try to duplicate the Hodgdon recipes.
This is layer upon layer of errors.
I cut to the chase, ream out my 38 specials, work up a load with slow powder until the cases stick, and then back off a safety margin so the cases will not stick.
I have no use for Hodgdon data, but I am putting their powder in my modified revolvers.
I make up my own loads.

I can tell you in most cases CUP numbers are higher than PSI numbers, sometimes by a lot. While 35,000 PSI is the piezo limit I've seen Copper Crush limits above 43,000 CUP.

SAAMI's standards are voluntary "guidelines"...not law.
Accurate has several 357 Mag loads that exceed 35,000 PSI

I can tell you in most cases CUP numbers are higher than PSI numbers, sometimes by a lot. While 35,000 PSI is the piezo limit I've seen Copper Crush limits above 43,000 CUP.

Have never understood why in most cases, CUP pressure levels are higher in handgun rounds than psi pressure levels (relative to each other), yet psi pressure levels are almost always higher than CUP pressure levels in bottleneck rifle cartridges? Seems counterintuitive, but that's the way it is.

Don

Accurate has several 357 Mag loads that exceed 35,000 PSI

Are those loads for the 357 magnum or 357 maximum? The actual 357 magnum MAP is 36100 psi, the 357 maximum MAP is 40000 psi