Big Changes in Load Data Hercules 1987 to 1992 - Why?

[Low Budget Shooter]

I've been looking through old load manuals, trying to tweak some of my .38 Special and .357 Magnum loads with the powder I've been able to find in stock. I found that the load data in Alliant 2005 is just carried over from Alliant 1995, which is carried over from Hercules 1992. But there were big changes in the tables between Hercules 1987 and Hercules 1992. For example,

Hercules 1987 has the following for .38 Special 158 grain RNL:

Red Dot: 4.0 gr for 925 fps
Unique: 5.5 gr for 980 fps

Hercules 1992 has the following for .38 Special 158 grain SWC:

Red Dot: 3.1 gr for 835 fps
Unique: 4.3 gr for 920 fps

Those are drastic reductions in powder charge! Why the difference? Were the powders reformulated, or the testing equipment changed, or what?

Snapshot of the pistol page from 1987 and 1992 attached.

Thanks,

LBS

147783

[35remington]

The old Unique data is above Plus P now. The old Red Dot is Plus P.

Correct data is 4.7 Unique standard 5.3 Plus P.

The old data is a bit heavy, the newer slightly light. See newest data for correction.

[Low Budget Shooter]

35r, do you know what went on at Hercules to arrive at the new data?

[35remington]

Different pressure standards the powder did not change. Look at latest data with Speer brand bullets online.

[Bigslug]

When was the last time Fish & Game authorized a culling of the lawyer herd? I'd wager it was prior to 1987.:roll:

[Low Budget Shooter]

Funny :)

[376Steyr]

Biggest change in reloading data was due to changing in the way pressure was measured, from the "crusher" method which, in simple terms, measures "average" pressure during powder combustion to the electronic piezoelectric method, which can measure "peak" pressure. It turned out a lot of the older loads exceeded the industry standard. A couple of years ago, Alliant (son of Hercules) pulled all their data for Blue Dot in the 41 Magnum, when new testing showed the old published loads, which had been used for years, was over the industry standard.

I have an old Speer manual somplace , from around 1964 I think, that shows 9.0 grs of Unique (!) with a 250 Keith as max for the .44 Special.

This somehow seems appropriate: "Measure it with a micrometer, mark it with a grease pencil, and cut it off with an axe"

[Cmm_3940]

When did the copper-crusher method of measuring pressure fall out of general use? My understanding was that data got changed because modern internal ballistics test gear measures total pressure, but copper-crusher can only measure peak pressure.

[376Steyr]

When did the copper-crusher method of measuring pressure fall out of general use? My understanding was that data got changed because modern internal ballistics test gear measures total pressure, but copper-crusher can only measure peak pressure.

I believe you have that backwards.
This Wikipedia article goes into more detail: https://en.wikipedia.org/wiki/Copper_units_of_pressure

Key sentence is: " Since a longer duration, lower pressure pulse can crush the cylinder as much as a shorter duration, higher pressure pulse, CUP and LUP pressures frequently register lower than actual peak pressures (as measured by a transducer (https://en.wikipedia.org/wiki/Transducer)) by up to 20%."

[Cmm_3940]

OK, I knew that CUP was registering too low, but was thinking of instantaneous measurement at peak pressure with CUP, vs. pressure(Δt) with the transducer. The other way around makes more sense if it takes a certain Δt for the copper cylinder to actually deform.

[MtGun44]

I don't know that this was when they shifted pressure measurement technology, but it is likely
what happened.

Crusher methods are not really ONLY measuring peak pressure, where the piezo transducer reacts
quickly enough to give a pressure vs time plot, so suddenly better data let them see what was
going on more accurately.

SAAMI sets pressures, and as they found out that the old methods were inaccurate, they used the
newer and more accurate info to stay inside SAAMI pressure limits.

All that said........ did any guns get blown up with the old data?

Not likely. Don't sweat this with a modern gun.

In a marginal design, use the modern data.

Bill

[Low Budget Shooter]

Thanks for all this info.

[44man]

If you notice all books and on line loads are still CUP.

[44MAG#1]

Speers latest manual #14 is listed in PSI in both load levels. 17,000 PSI and 20,000 PSI.

[44MAG#1]

Also Speers #13 says loads are held to 17,000 PSI and 20,000 PSI respectively.

[warf73]

Can't remember for sure but that might have been time frame that Alliant changed to their NEW CLEANER formula. I still use the same powder bushing in my Mec. I looked at the time and seen no differents in powder bushing call out according my books.
But Alliant went through and changing all there fast powders (pistol/shotgun) to a new cleaner formula. Not sure if they did the same with rifle powders at the same time. It took a year or so for all the bottles to get changed if I remember right.
Might have been the same time frame were they went from paper bottles to plastic also not sure.