Old vs New IMR 4350

1

1972RedNeck

New member
I recently got a copy of Ackley's "Handbook for Shooters & Reloaders". Has some loads for 375 Weatherby using IMR 4350, which I happen to have a lot of from several years back when it was all I could find (still can't find much of any 4350 in my LGSs).

Is today's IMR4350 the same as the IMR4350 from the 1950s? I will obviously start low and work up - I just want to make sure it's close enough to start with...
 
Boy that's a tough one. Even if it were very similar I'd be concerned about how well it aged--you're talking about one of the more cavernous cases that loads near 100 grs of powder. If it were me, I'd just buy some new H4350 (yes, I know it's not exactly the same as IMR 4350) which is one of my top go-to powders for across-the-board outstanding performance in a multitude of cartridges. I'd also be careful about the low end of your loads just as much as the high end in a big case.
 
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Be skeptical of the data in P.O. Ackley's books, it is generally considered to be very hot. As far as I know, he didn't have access to pressure testing equipment to verify if those loads were within maximum pressure limits. Personally, I'd stick to published data that includes measured pressure, such as in the Lyman manuals.
 
I've been using top of the scale loads of IMR 4350 in my 30-06's since the 90's. If there's any difference between old and new it's miniscule.
 
Stagpanther,

I don't think the OP is saying his IMR4350 is from the '50s, but he is rather just asking if load data from then is applicable.


1972RedNeck,

I know the manufacturing location and processes have both changed since the '50s. I expect they try to keep the burning properties close enough for most legacy loads to work, but you want to instead use data from Hodgdon's website (which has your cartridge and loads with 4350) because they control the specs the powder is ordered to and, as you say, start low and work up.
 
If I were using recently manufactured powder, I'd use current load data instead of data from the 1950's if that data is different. Do that and you'll be fine. If you have a load that you like from the 1950's I'd not use it with current manufactured powder until I dropped down and worked back up.

I'd say chances are good that it will be fine, but I'd proceed with caution.
 
Stagpanther,

I don't think the OP is saying his IMR4350 is from the '50s, but he is rather just asking if load data from then is applicable.
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Got it--my bad--like you say I'd go to Hodgdon's site and use their data.
 
I know the manufacturing location and processes have both changed since the '50s. I expect they try to keep the burning properties close enough for most legacy loads to work, but you want to instead use data from Hodgdon's website (which has your cartridge and loads with 4350) because they control the specs the powder is ordered to and, as you say, start low and work up.
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I would love to, but Hodgdon does not list a single load for the 375 Weatherby with IMR 4350. They have one load for 375 H&H with IMR 4350.
 
If I were using recently manufactured powder, I'd use current load data instead of data from the 1950's if that data is different.
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The problem is, current load data isn’t exactly plentiful…
 
Best you can do is collect all the load data available and compare. Some of the books are crazy hot and others are cold having a decent amount of grains between them. I load my 3006 hot with imr4350 and it pretty much matches the winchester load for weight and speed.

Sounds like it's going to be trial and error.
 
I would love to, but Hodgdon does not list a single load for the 375 Weatherby with IMR 4350. They have one load for 375 H&H with IMR 4350.
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Which is why I recommended H4350--which they do list (they also market IMR 4350, maybe that tells you something). You'd probably be OK with IMR 4350 (I've used them interchangeably with the knowledge they are not identical on smaller cartridges) but considering it's a large magnum I wouldn't swear on that for the big Weatherbys.
 
H4350 is temperature insensitive with about 8 fps change from 0 to 125 def F. (0.064 per deg. F which is pretty linear).
IMR4350 is temperature sensitive with about 155 fps change from 0 to 125 deg F. (1.24 fps per deg. F).
Most US load tables are based upon 59 deg. F. European tables are based upon 70 deg F. which complicates your choices a bit more.
Both are good powders, but the more you know about them, the better you can plan you reloads.
In my 6.5mm CMs, H4350 performs more accurately (0.322 for 273 5-round groups compared to 0.362 for 71 5-round groups).
As you can see, once I gathered statistically significant data, I shoot what is the most accurate.

If you live in a place with big temperature swings during the day, you have to pay attention to the temperature when you are loading a temperature sensitive powder, especially if you like to load near Pmax.
 
The OP has lots of IMR 4350 powder and a Weatherby 375, but not much data for the combination of the two.

The P.O. Ackley books just list "4350" powder, which I recall was military surplus, not sure if that equates to the IMR 4350 or H4350 powders we have today.

The Hornady Handbook 7th and 9th editions have data for the 375 Weatherby with IMR 4350, for 270 and 300 grain bullets. I suspect that other editions of the Hornady Handbook have data for the 375 Weatherby also. Surprisingly it's not much different than P.O. Ackley's data. Unfortunately Hornady doesn't publish pressure data in their handbooks. :(

Quickload does support the 375 Weatherby and could be used to check the existing limited data for this combination, if all the program inputs are known.
 
The P.O. Ackley books just list "4350" powder, which I recall was military surplus, not sure if that equates to the IMR 4350 or H4350 powders we have today.
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In the section where he talks about powders used, Ackley says it is IMR 4350. And in other calibers, the 4350 load data is nearly identical to modern IMR 4350 load data.
 
( Unfortunately Hornady doesn't publish pressure data in their handbooks.)

none of my nosler-7 hornady 19 21 23 books have a listing for the 357WbM but all have pressure data for other loads.
strange.
 
1972RedNeck said:
I recently got a copy of Ackley's "Handbook for Shooters & Reloaders". Has some loads for 375 Weatherby using IMR 4350, which I happen to have a lot of from several years back when it was all I could find (still can't find much of any 4350 in my LGSs).

Is today's IMR4350 the same as the IMR4350 from the 1950s? I will obviously start low and work up - I just want to make sure it's close enough to start with...
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Ackley Data should be close if rifle is a WBY rifle with freebore.
 
CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

1972RedNeck said:
I would love to, but Hodgdon does not list a single load for the 375 Weatherby with IMR 4350. They have one load for 375 H&H with IMR 4350.
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My bad. They have H4350 listed. It's not the same, but it's very close on peak pressure for a given charge weight in this chambering. In GRT (for which both powders, but especially the H version, have received a fair amount of Pressure Trace feedback), with the 270-grain Speer bullet, multiplying the H4350 charge by 0.994 gives you a pressure matching IMR4350 load.
 
In GRT (for which both powders, but especially the H version, have received a fair amount of Pressure Trace feedback), with the 270-grain Speer bullet, multiplying the H4350 charge by 0.994 gives you a pressure matching IMR4350 load.
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Thank you. I will add this into my safety checks for this cartridge.
 
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