I'm looking at loads for the 270. Some recipes call for H4831 and some for IMR4831. Are they very close in performance? Are they interchangable?
I've got H4831.

I have never used IMR4831 but from what I have read they are similar in burn characteristics as well as burn rate. The data is not interchangable and I believe an accurate load can be achieved with either of these powders in 270 Win. I have used H4831SC in a lot of calibers from 243Win through 338RUM and have had good to very good results with it. I call it my go to powder.

they are not interchangable go to hodgdons website they have the loading data your looking for

Just in case you didn't know, Hodgdon now owns IMR. They are not interchangeable but very similar. I have worked up excellent loads in all of my 270's with each.

If you have H4831, you do not need to purchase the IMR unless you just want to.

57.0 grains of H4831SC in my brother's 270 yields extraordinary groups with a 130 Btip. He has a 25.5" PacNor barrel too.

H4831 is probably THE top powder overall for a 270. My other favorites are Re19 and Re22.

They are both very very well suited for the
.270 win.I got good results with with the both
and IMR and every powder I shot from my .270
rifles.

I shot the following load for years.
58.0 grains of H4831
140 grain Hornady boatail spire pt.
CCI#250 primer
any brass (I prefered Winchester).
I got 3050 fps with a Ruger #1 B single shot
and killed Deer,Elk,Bear,Antelope,and praire dogs with it.You cant go wrong with it.


I have been shooting the next load for a few
years and have had very good results also.


56.5 grains of IMR-4350
130 grain Winchester power point
CCI#250 primer
Winchester cases
3087 fps from brass shot 3 times fired with this load in a model70 clasic feather wt. 22"
barrel.



whatever you choose they will all shoot good with this caliber unless you got a bad one.
(slim chance though)

in burn rate I found IMR 4831 to be about half way between 4350 & H 4831

When the IMR version was introduced, Hodgdon was still selling the original military surplus version. At that time, the Hodgdon version was signigicantly slower than the IMR version, in fact, the surplus 4831 was almost as slow as today's IMR 7828.

The surplus powder is long gone (except for a few hoarders like me). When Hodgdon ran out, they started purchasing powder made to 4831 specs by various manufacturers like ICI from Scotland and now ADI from Australia. To further complicate matters, H4831 now comes in two different versions which, despite advertising hype, cannot help but vary slightly from one another in internal ballistics characteristics.

The bottom line is that IMR 4831 continues to be closer to IMR 4350, and H4831 contiues to be slower -- more comparable to the surplus 4831 of old (though still a tad faster). I like the slower powder in the .270, so I would suggest sticking with your H4831.

BTW: It seems as if there are very few applications in which IMR 4831 gives a better pressure/velocity ratio than IMR 4350. If I were using the IMR line, I would likely opt for 4350 in most instances. But with a .270 using bullets of 130 grains or above, I would suggest IMR 7828 over either of the other IMR powders.