Old vs New IMR 4350

I don't know just how much help this might be but, when Ackley did his book, IMR 4350 was made by DuPont using nitrocellulose made with cotton linters here in the USA. DuPont later sold their powder manufacturing business to a company using the name IMR. IMR decided making nitrocellulose with cotton linters was too expensive and went to using wood, basically sawdust. It works just as well but it is my believe that it causer IMR 4350 to be a hair faster burning. You might not even notice it until approaching max loads.

One of my rifles is a .375 Chatfield-Taylor, also known as the .375 Taylor or .375/338 Win. Mag. Wildcat. I worked up a load for the270 and 300 gr. bullets using Ackely's data with the DuPont and IMR versions and reached Ackley's load level with both types with no apparent change in pressure other than a slight velocity loss with the current type of 4350.

Velocity was slightly higher than the .375 H&H and accuracy was superb. Velocity had very small extreme spreads. Recoil in my rifle which only weighs 7.5 pounds is rather substantial. I designed it that way for a steep mountain hunt in dark timer. That hunt never took place due to a falling uot with the outfitter. Still haave the rifle.

If I were working up a load for the .375 Wby and had only Ackley's data to work with, I'd drop back from his max by about 2.0 to 2.5 gr. and work back up a half grain at a time.
 
Yes, the wood has resins in it, and they tend to make for less clean-burning nitrocellulose, so carbon fouling goes up, and the oxygen balance gets a little more negative, so energy conversion per unit weight drops a little. Lots of folks fall in love with Vihtavuori powders, despite their cost, just because they still make their own nitrocellulose from cotton, and it makes for cleaner-burning powders.
 
Yes, the wood has resins in it, and they tend to make for less clean-burning nitrocellulose, so carbon fouling goes up, and the oxygen balance gets a little more negative, so energy conversion per unit weight drops a little. Lots of folks fall in love with Vihtavuori powders, despite their cost, just because they still make their own nitrocellulose from cotton, and it makes for cleaner-burning powders.
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I work a lot with conservation grade papers in printmaking--I have no idea if there is any relationship or not to the smokeless powder world--but paper made with pure cotton lignin is acid-free over time; whereas paper made with wood cellulose is highly prone to acidification unless buffered with other chemicals.
 
That must be a difficult round to find data on, checked all my books going back to the 1965 Shooter's Bible, just H&H tables. There was one which has a .375 Winchester but no Weatherby unfortunately.
 
If I understand correctly, the numbers like IMR 4350 and H-4831 indicate a specification for the Military. "IMR" stands for "Improved Military Rifle" and "H" stands for "Hodgdon".
Back in the latter 20th Century, IMR meant DuPont was making it as new powder and"H" meant Bruce Hodgdon was salvaging it from military.

This is roughly concurrent with PO Ackley data.
We always realized IMR 4350 and H-4350 would have slightly different load data.
Understand selling reloading powder is a different business than selling ammunition.
The ammo manufacturer can receive a train car of a designated powder and test it, and make adjustments so that lot of AMMO will perform as expected.
Charge weight might vary batch to batch.
Selling POWDER the reloader might buy a pound,load from it for 3 hunting seasons, buy another pound and use the same "Old Trusty Load"

Its the POWDER the manufacturer tries to keep reasonably consistent.

A few decades after the last big war, Bruce Hodgdon started running out of military surplus powder, . We were still a market for 4350 and 4831 so there was a big,well publicized shift to "Newly Manufactured Hodgdon Powder" and the packaging was labeled as such. Hodgdon went out of his way to educate us that "Newly Manufactured Hodgdon Powder" WAS NOT the same for load data that would be found in PO Ackley.

A friend brought me a 30-06 Mauser Sporter his Dad built. "I was gonna use this hunting so Dad had his old Elk Hunting Buddy load up some of the same ammo they used to use but it kicks really hard and there was this black stuff and looky,that hole where the primer goes is all splayed out and the primer is gone!

I told him "Don't shoot any more of those" Out of curiosity I broke down a loaded round and weighed the charge.
It seemed like the Old Buddy loaded up a perfectly safe and normal load for H-4895 Surplus but it was H-4895 Newly Manufactured. Overpressure.

Now,Old Hogdon 4350 is not Old DuPont 4350 . DuPont isn't even making powder. The IMR 4350 of the PO Ackley is not the IMR4350 of today.

I've spent a lot of time in the "Ackley's Handbooks for Shooters " and there is good stuff in there.....published when?? Over 60 years ago?

I might use the data to get in the general area of a load but I won't load to Ackley Data. Its too old and the power is made by different people in a different place.

Years past,I have called Hodgdon or Nosler or Sierra and asked for a "Tech Rep" Sometimes they are helpful with current load data but they won't tell you on the phone. They would snail mail it. Maybe they still give support.

You might try Weatherby.

I believe Norma was loading the Weatherby Cartridges. They might be able to help you.

Isn't the 375 Weatherby just a 375 H+H Improved? (Sensible cartridge!) then the 378 is a whole nuther beast.
 
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