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Looking through one of my old books. Speer # 5 from 1967. I have a 4831 question. I don't use a lot of it but have some. Data in the book simply lists 4831. Does not specify IMR or Hodgdon. On page 27 a brief description is given. It's listed there as Hodgdon IMR 4831. I've looked at 3 different burn rate charts and have 3 different listings. Can anyone enlighten me on this?
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Some "4831" history here;
https://czfirearms.us/index.php?topic=62930.0
If (now) close to 60 years ago that Speer#5 would have been talking about IMR4831 -- as it existed then
4831 started out as a Military powder. After WWII, it was sold to reloaders as Mil Surp.
Anyway, Use the current data for the powder you have.
Many older reloading manuals have loads that are way over max compared to the newest manuals. Whether this is due to the change from measuring pressure in CUP vs PSI or corporate lawyers can be debated but it is a good idea to start at max -20% if the charge seems high. I have used loads from the older books that clearly maxed out way before getting to the older published max. And others for a 7mm Mag where I use 8 grains! over the new books max with no pressure signs and the correct velocity (and it could be 4831). Turns out some 7mm mags were made with short throats so every reloading manual drastically dropped their max load but since mine has a longer throat the old loads are OK.
IMR 4831 & Hodgdon are NOT the same. H4831 is a bit slower so data is NOT interchangeable. Why I cross ref several data sources. The Hogdon/IMR website is a good source for cross ref with any manual.
https://hodgdonreloading.com/rldc/
Cannister IMR 4831 was not available to reloaders in '67. All "IMR" 4831 was military surplus Back then. It wasn't until the '70s when stocks of milsurp 4831 began drying up that Hodgdon contracted for newly made 4831 with the same burn rate as the original milsurp IMR 4831. Hence the "H" designation for Hodgdon's 4831. A few years later Dupont began making their own cannister version of 4831 for sale to reloaders...Hence the different IMR 4831 designation on that powder. New IMR 4831 burns a little faster than does newly manufactured, or the original milsurp [I still habe 8 pounds of original milsurp 4831 in excellent condition] so the load data is not interchangeable with data for H 4831.
Do NOT use old Speer data. Many over pressure, maximum loads.
I don't ever start with maximum loads. I start low and work my way up till I get my desired results.
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Somewhere in GONRA's Junque Pyle
is a loose leaf folder of WW II era IMR 4831 data,
lot nrs, charge wt. etc. for is original application:
20mm Oerlikon auto cannon.
If both imr and hodgdon is listed the data must be good for both. I would use it myself. But try a newer manual.
If you start with the starting loads and work up like you are supposed to it won't matter which 4831 it is. The starting load on either one will be low enough you shouldn't get in trouble. I have seen a few max loads listed in old Speer manuals that won't even fit in the case. So if the load in the older manual is a lot higher than a new manual I would start with a start load in the new manual.