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  #1  
Old 04-11-2005, 11:31 AM
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Question Does DuPont = IMR?


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Have decided on my Spring reloading project:

Use load data from old Jack O'Connor books and articles to work up loads for my rifles ('06, 35 Whelen). I might even get the itch to purchase a 270 Win. Who knows where this will lead.

Question for you veteran reloaders:

When Jack refers to DuPont powders, like 4320 and 4350, can I assume that the corresponding IMR powders are equivalent?

I am wise (?) enough to start 10% lower than the loads O'Connor lists, no matter what. But I am curious about how closely current production powders correspond with those from the early 1960's.

I am all ears, Gents...
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  #2  
Old 04-11-2005, 12:24 PM
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It's generally thought that the IMR powders, made by Expro in Quebec, are about 5% faster than the old DuPont powders. This is due to a change from cotton linters to wood linters for the production of nitrocellulose. I suspect that 4320 is faster now, but as I'm out of the C-I-L primers I used with DuPont powder, I can't say for sure.

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  #3  
Old 04-11-2005, 12:51 PM
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Yes. One thing to be acutely aware of, though, is that according to a story i read, his scales read high. The writer (I don't remember who, but think it was someone like Petzal..) never could understand how O'Conner could load the amounts of powder he did without getting seriously over-pressure. After Jack's death, his scales were checked and found to read two grains heavy, so when he was talking about 50 grains of powder, it was actually 48. I've never tried any of O'Conner's load data, so i don't personally know, but you might want to compare it with some current manuals to be sure.
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Old 04-11-2005, 01:20 PM
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IIRC, John Amber, long time editor of Gun Digest, sent a set of check weights around to a number of gunwriters. O'Conner didn't believe the check weights.

On the other hand, Hatch's version may be the correct one.

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  #5  
Old 04-11-2005, 01:43 PM
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And it may be that they're both correct, just at different times. The important thing, tho (IMO), is to compare with a couple of current manuals to make sure you don't overload to start with.
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Old 04-11-2005, 02:56 PM
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Yup, Dupont and IMR. Just as a side note, Hodgdon bought IMR powder 16-24 or so months ago. They have said that they are not going to change formulations. I have noticed that IMR is turning up in the Hodgdon type plastic bottle lately.
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Old 04-11-2005, 03:00 PM
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Yep..start low (10% is a good guesstimate...but if the first shot tells you to back off, then back off). Some of the IMR's during this time frame were real live GI surplus...sold out out great big brass powder cans into whatever container you brought to the gun shop.
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Old 04-11-2005, 03:47 PM
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Thanks for the replies. You all are saying about what I expected.

I have done some initial comparison with current manuals. In some cases O'Connor's loads are above currently listed max loads; in other cases they are a little below max.

I, for one, am not concerned about maximum velocity no matter what source I use for a starting load. When I find a load that shoots accurately and has a velocity within a good working range for the caliber/bullet-type, I stop. For instance, if I can get a .308 Hornady or Speer PSP 180 gr. bullet to group well in the 2500 to 2600+ fps range, I'm happy. It doesn't take 2700+ fps for me to feel like I have a good 180 gr. '06 hunting load.

Thanks again. I think this will be fun.
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Old 04-11-2005, 05:20 PM
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Quote:
Originally Posted by naumann
Thanks for the replies. You all are saying about what I expected.

I have done some initial comparison with current manuals. In some cases O'Connor's loads are above currently listed max loads; in other cases they are a little below max.

I, for one, am not concerned about maximum velocity no matter what source I use for a starting load. When I find a load that shoots accurately and has a velocity within a good working range for the caliber/bullet-type, I stop. For instance, if I can get a .308 Hornady or Speer PSP 180 gr. bullet to group well in the 2500 to 2600+ fps range, I'm happy. It doesn't take 2700+ fps for me to feel like I have a good 180 gr. '06 hunting load.

Thanks again. I think this will be fun.
naumann - that's my school of thought too. I'll give up a few feet per second any day to have all the bullets go in the same hole. It's nice to get the best of both worlds but I generally find the most accurate loads are a grain or two below max. One thing I always do is find a compressed load for all my cartridges. I have gotten into the habit of keeping powders for different cartridges in different parts of the reloading room along with their cartridge specific tools and components (dies, trimmers, bullets, etc.) that way it's almost impossible for me to screw up a load. Never more than one powder on the bench at the same time.
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  #10  
Old 04-26-2005, 03:13 PM
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It's always a good idea to start low and work up. The percentage to me depends on the powder i.e. 4350 4064 etc.etc. The slower the powder burns the less you should have to reduce the load unless you are working with a can somebody else opened then pitch it and get a new one. I still use loading data from an old Lyman book #23 I think. I do know that Dupont used to make IMR then IMR made IMR now Hodgons makes IMR so all the data should be pretty close.
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  #11  
Old 04-27-2005, 07:25 PM
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I just loaded some IMR IMR 4350 a couple of months ago in 7mm Mag. I used the same load I have used since the middle '60s and it shoots just like it always has.

I checked some IMR SR 4756 against some DuPont SR 4756 last year. The DuPont was at least 20 years old and the IMR was two months old. It was the same stuff.

I'll probably do the same comparison with some IMR 3031 using a Lyman 311291 in a Handi rifle .30-30.

So far, the only difference noticed has simply been lot to lot variation.
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  #12  
Old 04-28-2005, 09:43 PM
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Thanks for all the replies.

In the meantime I ran across a book on handloading written by Col. Townsend Whelen, 1957. He refers to the powders as "Dupont IMR."

BTW, I'm having fun reading the Colonel's book. It covers all the basics, whys, and wherefores of loading for centerfire rifle and pistol ammo. (Don't recall the exact title right off and the book is two stories up from the 'puter desk.)

At any rate, the Dupont/IMR lineage is obviously intact. Even so, I'll start below listed max, no matter where I get the load data, and let my rifles and Chrony tell me when I have the load I want.
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