What is the difference...?


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antichrome
November 16, 2006, 06:14 PM
Please forgive my ignorance, but what is the difference between H4831 and IMR 4831? :o I've been loading 46gr of H4831, CCI magnum primer and 100gr Sierra Spitzer in .243. :eek: Yes it's hot.....borderline too hot but shoots 1/2 MOA at 100 yds. I'm about out of H4831 but have a couple of pounds of IMR 4831. My very old Sierra reloading book only refs 4831, no "H" nor "IMR".

Thanks,
~ac

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ocabj
November 16, 2006, 06:28 PM
http://www.hodgdon.com/data/general/burnratechart.php

Different burn rates. While it is named the same, it is produced by different companies. Although, Hodgdon did buy out IMR Powders recently (as well as Winchester powders). Either way, they are considered different powders and you should develop loads using data for that specific brand of powder.

Jim Watson
November 16, 2006, 07:03 PM
What Hodgdon got was the US distributorship for IMR and Winchester powders. They don't own the factories in Canada and Florida, respectively. Hodgdon Spherical powders are minor variations on Winchester Ball powders out of the same factory in St Marks, Florida. Hodgdon flake and extruded powders are now made by ADI in Australia.

Back to the original question.
Hogdgon started out selling surplus powders including 4831. It was really IMR4831 made for 20mm ammunition. When surplus stocks ran out, they went to ICI-Nobel in Scotland and had it copied with as near the same burning rate as possible. Now they have gone to ADI for H4831. The burn rate is near enough the same for normal load practices.

But when DuPont released fresh IMR 4831 through their channels, it turned out that it was a bit "faster" than H4831, either surplus or repro, and CANNOT be loaded the same as any H4831. DuPont said they did not change the specs on their production of 4831, that Hodgdon started out selling old powder that had lost some zip and then had that copied.

So the short answer is, use IMR data for IMR powder and Hodgdon data for Hodgdon powder, even if of the same number. You can find it all from the Hodgdon website these days anyhow.

antichrome
November 17, 2006, 09:20 AM
Thanks Jonathan for the link. The Co. firewall is making me wait 'till I get home to check it out.

Thanks Jim for your response. It's good to know the history here as all of my rifle powder was bought in the late 70's. Guess you can tell it's been a while since I've re-loaded.

~ac

The Bushmaster
November 17, 2006, 09:53 AM
Antichrome...Did you say you had an "very old Sierra loading book"? Might I recommend that you buy a new up to date loading manual? Just a thought...:)

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