What is the difference in IMR 4831 and H4831? They are side by side on Lee's burn rate charts. Can you substitute one for the other?

Also, what is the difference in IMR 4895 and H4895? They are separated by only RL12 in Lee's burn rate chart. H4895 is shown as just slightly faster burning than IMR 4895. I am assuming you can't substitute these two for one another.

The 4895 and the 4831 powders you mention are similiar to each other but they are different powders with different burn rates. Although the names are nearly identical that's where it ends for reloading. You will end up with in a grain or two if you work up the 4895's and the 4831's but please don't just do a one for one substitution.

I believe that H4895 is slightly slower than IMR 4895 and IMR 4831 is a bit slower than H4831 but could have this wrong and someone with more knowledge will chime in an correct me.

Here's a great site to review them both for the cartriges you are interested in:

http://stevespages.com/page8a.htm



The Hodgon powders are advertised as being less temp sensative and have shorter grains which can make metering easier.

there is very little difference in the 2-4895s but there is a good bit of difference in the 2-4831s.. H- is slower.. most of the time 4895 can be cross referenced in load data... the 4831 cannot

I recently did some experimenting with H and IMR 4895 powder, using a 222 Rem Mag.
I loaded the same load of each powder, and got great results with the H-4895, and not good accuracy with the IMR-4895. Your rifle may experience exactly opposite results. My point here is they are not the same powder.

At one time, both H-4895 and H-4831 were milsurp powders. At the time, IMR-4895 and H-4895 were for all practical purposes interchangable just by starting with the starting data for either one and working up. You probably could still do that, just be careful. St one time 4895 was strictly milsurp and you could buy it through the DCM. it was a data powder and could be as fast as 4198 or as slow as 4320. When you bought somwe. it came with a data sheet telling you to use 4198 data, or 3031 data, I think you get the picture. I think Hodgden bought up all the milsurp versions of 4895 and blended them into one usable powder and then furnished data. IIRC, the H version was a hair slower than fresh made 4895 by Du Pont but they were interchangable for all practical purposes.
The 4831's were a bit different. Hodgden's milsurp 4831 was quite a bit slower burning than the IMR version as it had deteriorated somewhat due to age. Hodgden then had a replacement powder made in IIRC Scotland that duplicated the slower burning milsurp version. As stocks of milsurp were rapidly either being used up or deteriorating to where it was unusable, Du Pont started making up fresh powder according to the original formula which produced a powder that was faster burning than the milsurp that had aged.
The 4895 powder is hard to trace as far as it's history is concerned. I'm thinking some time around 1937 when Du Pont brought out all the other Improved Military Rifle powders but can't find any information to corroborate my thoughts.
All I do know is the powder varied widely in burning rate from as fast as 4198 to as slow as 4320 with the arsenals adjusting accordingly
Paul B..

It's a real frustration that Hodgdon (who is the sole distributor of both the "H" and "IMR" brands) don't fix this.....if they're the same say so and discontinue one of them.....if they are not then change the number on one of them to eliminate the confusion......the idea that because they have the same number that they might be the same is an idea that needs to end.....and Hodgdon can do so and should.

Most folks know that H-4831 is quite a bit slower than IMR-4831 but there remains those that think many of the other numbers are identical powders.......and they just might be...but only Hodgdon can solve this!

I don’t have an exact comparison between H4895 and IMR 4895. My load testing with IMR 4895 was in a different rifle and using the 168 SMK. However, based on my experience with kegs of IMR 4895, the velocities with H4895 were higher than if I used IMR 4895. The 40.5 grain load below, I would have expected that with 41.0 to 41.5 grs IMR 4895.

Also, H4895 is green, IMR 4895 Black. (I don’t know is that is significant)



IMR 4895 appears to be slightly shorter grained.



Ruger M77 MKII
26 " Barrel 1:10 twist

174 FMJBT 40.5 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F

Ave Vel = 2559
Std Dev = 14
ES = 50
High = 2589
Low = 2539
N = 11
good group

174 FMJBT 41.0 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F

Ave Vel = 2634
Std Dev = 19
ES = 50
High = 2657
Low = 2607
N = 6
good group



174 FMJBT 41.5 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F

Ave Vel = 2670
Std Dev = 3
ES = 9
High = 2675
Low = 2666
N = 5
good group

Thanks for all the great info. I had not substituted one for the other, but was curious as to what the differences were. I agree with Vapodog that Hodgdon should rename/renumber one of them. My guess is that there are some people who are using them as interchangeable.

I appreciate this forum so much, because there are so many people with some great knowledge about reloading (and a few who think they have great knowledge).

I was glad to see this post this morning when I got to AR. I am new to reloading, only been doin it about a year now, and almost substituted the H-4895 for the IMR-4895 this weekend on some .223, figured I would wait and ask someone today on AR this mornin.

Thanks Red C. for the post,
Ben

IMR4895 is a bit slower than H4895, so you should not subst. IMR data w/ H4895.
H4831 is slower than IMR so again, you should not subst. H4831 w/ IMR data.