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Old February 24, 2013, 08:57 PM   #1
stu925
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New manual load data question

For about the last 15 years or so I've been using IMR 4320 in my sporterized 6.5x55 Swede (I'd rather not post the exact load as I'm not at all sure it'd be a safe load anymore). Recently I picked up a new Lyman manual (49th edition) and was looking at the 6.5x55 Swedish section and noticed that IMR 4320 is no longer listed. My question is why? Did they change something in this particular powder that makes it no longer suitable for this cartridge or is it just a case of there being better powders to use now? I plan to pick up some new powder anyway to load for the Garand I just ordered from CMP so if I need to work up a new 6.5x55 load it's not a huge issue but I really like the way that 4320 load shot and it always dumped deer in a heap. Guess what I need to know is if I need to start looking for a new load or not. I suppose working up another load for the rifle probably wouldn't be a bad idea anyway just so if I can't get 4320 I have something to fall back on. Your thoughts on this subject as always are appreciated.

Stu
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Old February 24, 2013, 09:39 PM   #2
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I have found the same issue when going from an older manual to a new one. The powder won't change, they would change the name or discontinue it first. Their liability would be to great. With all the new powders on the market they can't list them all so they drop some. When I have been faced with this issue, I review other new manuals and sure enough there is my powder and same weight bullet and my load is always not quite to their max load so I just go on my marry way.
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Old February 25, 2013, 01:48 AM   #3
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You could also check the powder manufacturer's website for their current data for that particular powder and cartridge. It could be that their current batch of that powder is slightly different than the older batches and they have changed their recommendations for their current powder. If it is no longer listed, I would contact them and see if they can give you any advice. On the other hand, if you have been using your loads without incident and no signs of high pressure, you choose to continue with your current powder and loads until your powder supply is exhausted. Once it is gone, you may want to try a powder that is currently recommended for your cartridge that has multiple data sources available.
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Old February 25, 2013, 04:22 PM   #4
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People who publish manuals want to sell them, even to customers who have bought one of their previous manuals. In order to do that, the new manuals must have something that the older ones do not. These days, with so many new bullet designs coming out, getting new info into manuals isn't so hard. But, previously, there were a lot of new powders coming out, and data on those was an attraction for repeat customers. I think that has a lot to do with which powders get dropped and which get added.

In a few instances, previously published loads have been found by experience to be bad ideas. "Blue Dot" powder in some .357 Magnum loads in one example. In those situations, there is usually some sort of public posting about the data no longer being recommended.

So, if you do not see anything saying that old data for a particular application has been found to be inadvisable, I think you can just continue to use the old data if there is no new data available.

Of course, when you buy more of the powder, the lot number will probably have changed and that means that you should drop the charge back and work-up again. Besides safety, you may find that the most accurate charge weight has changed when the lot number changed. Or not.

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Old February 25, 2013, 04:56 PM   #5
buck460XVR
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On their web site reloading data, IMR doesn't list 4320 in any load recipes for any bullet weight in 6.5x55 Swede, altho they do list 4350. Same with Hornady's manual. If those two, along with Lyman don't list it, I would assume that it is not the most appropriate powder to use in that platform. At one time it may have been, but either the formulation has changed, or other powders have been found to be more appropriate. I would e-mail IMR for the reason as I have found them to give quick and courteous responses to any questions I have ever asked them.
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Old February 25, 2013, 05:29 PM   #6
Unclenick
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Given that Hodgdon has data for both faster powders, like IMR 4064, and slower ones, like IMR 4350, I'm not sure why IMR 4320 was left out. As far as Lyman goes, they only have so many load slots they develop loads to fill under each bullet weight, so they drop some and pick up some others as SL1 said.

But AFAIK, IMR 4320, like all powders Hodgdon distributes, is a canister grade, meaning it is blended with held back fast or slow lots of the same type of powder as needed to keep its burn rate within ±3% of their reference standard for the type. This reference standard is an exactly average lot of the powder type that they keep aside for QC and for load development. They currently do this with all the H and IMR powders they distribute. (I believe Winchester's standard is managed by Olin. I think that's the case because Hodgdon says the reason Winchester loading data is disappearing from Hodgdon's on line data is that Olin has not been keeping their proof of performance firing data current.) Bottom line, though, IMR 4320 should not be substantially changed. When you get a new lot number, drop the charge back to 90% of the old Lyman manual's maximum and work back up. Just 6 rounds separated by 2% of maximum is all it takes to check on pressure signs. More rounds fired in smaller charge increments is usually needed to spot accuracy loads, though.

Changing powder formulations does happen. Most often it's because the original plant sourcing the powder no longer produces it, so a second source has to be found who may not make it exactly the same, but it's not common and not true of the IMR line. As an example, if you look at the FAQ at Accurate, you'll see they are no longer able to get their Nitro 100 powder from the original supplier and the substitute has changed and invalidated their pistol data. But they are keeping the name.
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Last edited by Unclenick; February 26, 2013 at 08:09 AM. Reason: clarification
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Old February 25, 2013, 06:20 PM   #7
stu925
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Thanks guys I kind of figured it hadn't changed much but wanted to make sure. The load has been very good to me and will group 1" @100yds without much effort and as I said it always puts down the whitetails. Last one I shot flopped over backwards dead in it's tracks. I may work up another load for it just in case the 4320 is unavailable to me for some reason. Thanks again,

Stu
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Old February 26, 2013, 09:43 AM   #8
buck460XVR
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Just checked my latest Speer manual, and they too do not list IMR4320 in any load recipes for any bullet weight in 6.5x55 Swede, altho they do list 4350. Again....I would contact IMR iffin it was me.
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