IMR 4831 vs H4831 question?

C

Colten519

New member
The load data for the Barnes 100 gr ttsx I'm
Using calls for IMR 4831 and all I had access to was H4831. I know they are slightly different but was wondering if anyone knew how much. The IMR calls for a min of 60gr to a max of 64gr and was wondering if anyone could give any help on where to start with the hodgdon.

Thanks
 
I seem to recall that H4831 was "invented" by Bruce Hodgedon. He bought up several tons of surplus military powder designed for use in the Oerlikon anti-aircraft cannon. A 20mm BLOWBACK cannon design. A quote from Wikipedia:

The Oerlikon gun was installed aboard United States Navy ships from 1942, replacing the M2 Browning machine gun, which lacked range and firepower. It became famous in the naval anti-aircraft role, providing an effective defense at short ranges (in practice up to 1.5 km) at which heavier guns had difficulty tracking a target. The gun was eventually abandoned as a major anti-air weapon due to its lack of stopping power against heavy aircraft and against Japanese kamikaze attacks during the Pacific War.
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I remember buying 4831 scooped out of a 100 pound barrel for around 75 cents per pound back in the early 1960s. The surplus powder was so popular that when the supply ran out, Hodgedon contracted with some powder manufacturer to make it for him. DuPont noticed how well Bruce was selling the stuff and came out with IMR4831 which was supposed to have the same characteristics.

Were I working up loads, I'd use the manufacturer's data for the flavor I had.
 
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Solid copper would require a smaller powder charge, you might contact Barnes and query them and see if they have any load data for your caliber..

Barnes load data
100gr Barnes TTSX BT
Weatherby case
IMR4831 Min-60gr/Max 64gr
OAL 3.170"

This load data is available from Barnes website!! William
 
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Barnes site(decidedly limited. I think they really want to you buy their manual) also says to contact 'em for other data.
customerservice@barnesbullets.com
1-800-574-9200
There's 'H' data here, but I suspect it's lead cored bullet data. No idea where it came from. http://stevespages.com/257_10_100.html
There's also data on Reloader's Nest with the same caveat.
Not that it'll help much but the burn rate chart shows the 'H' to be a bit slower burning than the IMR. #128 vs #124.
Comparing the two powders in .257 Roberts(Just one cartridge with data for both powders.) with 100 grain lead cored bullets shows the IMR uses a tiny bit more powder to give much higher pressures(assuming Hodgdon's site is right. There are few anomalies there.) with about 300 fps more velocity in start loads. Max loads show higher pressures but very close velocities using .2 more powder and compressed loads.
 
I know they are slightly different but was wondering if anyone knew how much.
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There's a good bit of difference. For a 270Win, 130gr, H4831 lists 60gr as max and IMR4831 lists 57. For a 257 Weatherby, which is gross overbore, IMR7828 and some of the new RL powders (25 and 33) would be better choices. They are all slower than H4831.
 
I can't speak to your cartridge, but I have used both H4831 and IMR4831 in my .243 Win. at the same charge levels with no problems or signs of high pressure.

Note, however, my charges are in the lower 1/3 of the ranges given in the reloading books.

I can't recommend this for libility reasons, but if you must use the powder you have, I personally would start about 8 percent below the IMR4831 minimum and work up checking for pressure signs along the way.

Trivia qustion: Should DuPont named it IMC4831 as opposed to IMR4831? [Improved Military Cannon vs Improved Military Rifle]:D See my post above.
 
In my experience, and according to the charts, IMR4831 is faster than H4831. Don't do like I did and load the IMR4831 to the max load shown for H4831. Oooooo baby, that was a hot load. Do not interchange loads with those powders, and particularly at the top end of the load chart.
 
I have seen literally hundreds of reliable documents, many from all of the involved makers, that there is absolutely no cross manufacturer compatibility.
 
That's correct. It isn't just burn rate but the geometry of the grains and how many perforations they have that affects the curve.

On the link to Steve's Pages, the maximum load difference is about 3.5% higher for H4831. In QuickLOAD, using a 100 grain Barnes TTSX I get almost 8% heavier charge for the H4831. The difference could be based on different powder lots that were tested or a data source that's not got actual measured data. Looking in several other data books, I get as little as 2% difference between the two in some instances as as much as that 8% number in others. Additionally, QuickLOAD thinks the TTSX will use about 2% less powder than a Nosler BT to achieve the same peak pressure.

So, in your shoes I would take Hodgdon's data for H4831 with 100 grain jacketed bullet and reduce it 2%. Their data calls for 64 to 68 grains for the jacketed bullet. Reduced 2%, that would be 62.7 to 66.6 grains. I'm not sure why this range is smaller than the usual 10% difference in start to maximum, but based on what is in other manuals, Hodgdon's load is conservative, but it still fills the case near 90%. I would start at 62.6 grains and the bottom number and work up in 0.5 grain steps toward 66.6 grains, watching for an accuracy peak. You could creep past it, watching for pressure signs, but if you get adequate velocity and accuracy from the lighter load, there's no reason to put extra wear on the gun nor for burning its throat out sooner.
 
Colten519, I have Barnes manual #4 and I've seen their loading data that they post. In the manual for the 100gr TSX start load for IMR-4831 is 63gr @ 3358fps and max of 68gr @ 3547fps.

The new data they have posted they lowered all the loads by 3/4gr grains and dropped velocity 100fps +.

Wby factory ammo for the 257Wby list 100gr TSX @ 3570fps.
http://www.weatherby.com/media/weatherby/ballistics.pdf

Myself I would call Barnes and ask why velocity was dropped and difference could be test barrels used or the bullets.

I shot the 115gr 257 Wby and I used IMR-7828ssc
 
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