ot Changes in reloading data

[iceman]

Has anyone noticed how reloading data has changed over the years? Here is a small example. (all for 308 win 150 gr bullet IMR 4895)
Hodgdon manual circa 1986 also matches a Dupont release
42 to 44 for a max vel of 2794fps

Sierra 3rd edition circa 1989
41-44 for max vel 2700fps

Hornady 7th edition manual circa 2007
37 to 46.4 for max vel 2800 fps

Hodgdon web site present day
42 to 47.3 for max vel of 2920
What do you attribute the cahange to? Better methods of pressure reading, better velocity measuring? Before when reloading 308 I was just under the max of 44 grains (43.5) because 44 gave me pressure signs in my Savage 110 (ejector marks on case head). I realize that every rifle is different, but found it interesting there has been such a change in both load weight and velocity. Any comments?

[AJMD429]

With .357 Mag, I have heard the original load data was for higher pressure thresholds.
With .308, I don't think that would be a factor.
With .44 Mag using 2400, I've seen changes in the load data so much that what Sierra listed in the 1970's as a 'normal' load would currently be beyond 'maximum' - some have said the powder formulation changed, but I don't know if that was the reason for load data change.
Of course some of it could be the "lawyer factor"...

[COSteve]

The original 357mag pressure max was 40,000psi, now SAAMI says its 35,000psi. Lyman's No. 47 listed a max 158grn JSP load of H110 at 17.7grns, now they list it at 16.7grns.

If I were a cynic, I'd say that the lawyers have been busy convincing the manufacturers that fewer liability claims for less money are the result of lower max powder charges and what the heck, they can raise their prices per lb so they still make a ton of money with less liability insurance claims.

If I were an optimist, I'd say that the bullet manufactures are producing better products and the powder manufactures have found that lower pressures and lower velocities are now sufficient to get the desired performance. Or, I'd say that the powder manufactures have done more precise testing of their products with the newer methods and discovered that their loads were on the high side of the margins so they agreed with their lawyers and lowered their max charges to increase the margin of safety.

I'm a realist so I don't believe either position . . .

[iceman]

In this case the loads are increasing not decreasing. I didn't note the pressure readings if given, I will look into this when I get a chance.

[Terry Murbach]

LET'S THINK ABOUT THIS......DIFFERENT RIFLES......DIFFERENT PRIMERS.....DIFFERENT LOTS OF PROPELLENT....DIFFERENT LOTS OF BRASS....DIFFERENT LOTS OF BULLETS.....DIFFERENT TESTING GEAR.....MANY YEARS APART IN THE TESTING.....AND YOU EXPECT THEM TO BE THE SAME ??? I AM AMAZED AT HOW CLOSE ALL THE DATA YOU NOTED IS TO EACH OTHER. IT darn NEAR IS THE SAME WHEN YOU CONSIDER THE MYRIAD OF DIFFERENCES IN THE LOADS.
TAKE THIS TO THE BANK : IT WAS EXPECTED THAT PRESSURE WOULD VARY BY 5000lbs AT LEAST DURING EVERY TEST OF THE VERY SAME---VERY SAME !!!---COMPONENTS ON THE VERY SAME DAY. IT WOULD VARY THAT MUCH BETWEEN THE MORNING PRESSURE TESTS AND THE AFTERNOON PRESSURE TEST WITH THE IDENTICAL COMPONENTS AND DO IT EVERY FREAKIN' DAY !!!!

[Marc]

I have read several times that a lot of the changes in load data are due to better pressure reading equipment. Many rifle cartridges have had their data revised down wards. The other variables are lot to lot variations in primers, powders and cases and barrels.

[Old Savage]

What Terry said !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I did not know the specific on the 5000 lbs - thank you for that info.


AND WHY, YOU MIGHT SAY, AMATEURS SHOULD NOT BE MESSING AROUND TOO MUCH NEAR THE MAX.

[Sixgun]

LET'S THINK ABOUT THIS......DIFFERENT RIFLES......DIFFERENT PRIMERS.....DIFFERENT LOTS OF PROPELLENT....DIFFERENT LOTS OF BRASS....DIFFERENT LOTS OF BULLETS.....DIFFERENT TESTING GEAR.....MANY YEARS APART IN THE TESTING.....AND YOU EXPECT THEM TO BE THE SAME ??? I AM AMAZED AT HOW CLOSE ALL THE DATA YOU NOTED IS TO EACH OTHER. IT darn NEAR IS THE SAME WHEN YOU CONSIDER THE MYRIAD OF DIFFERENCES IN THE LOADS.
TAKE THIS TO THE BANK : IT WAS EXPECTED THAT PRESSURE WOULD VARY BY 5000lbs AT LEAST DURING EVERY TEST OF THE VERY SAME---VERY SAME !!!---COMPONENTS ON THE VERY SAME DAY. IT WOULD VARY THAT MUCH BETWEEN THE MORNING PRESSURE TESTS AND THE AFTERNOON PRESSURE TEST WITH THE IDENTICAL COMPONENTS AND DO IT EVERY FREAKIN' DAY !!!!

Dang, That Terry hit it on the nose. I was going to write that I have manuals from the 1920's on and some of those loads (especially for the 44-40) were downright dangerous, assumming that only a small percentage of people reloaded in a non-litigactious society, thus, the reason for changes in loading manuals, but.............science has come as long way.---Terry, you 'da man! --------------Sixgun

[Charles]

I am like Terry...I don't see all that much difference considering all the variable in the testing.

[AJMD429]

IT WOULD VARY THAT MUCH BETWEEN THE MORNING PRESSURE TESTS AND THE AFTERNOON PRESSURE TEST WITH THE IDENTICAL COMPONENTS AND DO IT EVERY FREAKIN' DAY !!!!

Very true - look at the velocity differences one gets with some powders merely depending on whether or not the muzzle was tipped up or down before firing...!

[444Hal]

I remember Hogdon uping the 45/70 loads for the Marlins a few years back.

[Canuck Bob]

There was a switch in supply for powders over the years. Lots of IMR and Hodgdon now comes from ADI in Australia. It used to come from Canada but they are shutting down our domestic shooting industry. It also became the Extreme brand for changes to better handle temperature variations. Supposedly the burn rate is the same but there has to be differences that amount to more than normal lot variation.

I once traced the recent history of IMR 4227 for my 32-20. It made my head hurt!