I'm working up loads for my 8mm Mauser k98 with H4350 and IMR4350. Hodgdon manual says 54 grs MAX(compressed) and IMR's web site says 43grs MAX. (150gr bullet)
The IMR at 43grs left chunks of what appeared to be un-burned powder residue in the barrel. The Hodgdon at 52grs was fine. Also the IMR at 43grs left my brass soot covered, which to me means a MILD load. Do these powders differ that much that there would be that much of a MAX load difference between the two? Is IMR being overly cautious in there load data?

That may well be a misprint. My sierra books shows 55grs of imr 4350 as max. There shouldn't be that much difference in the two. re-loaders used to use the two powders interchangably. Now they know there is a slight difference in the two.

Thunderbolt __

You are correct. The IMR loading is indeed on the mild side. Without chronography data, however, I can only speculate as to how much.

XMR 4350, IMR 4350, and H4350 are quite similar. On a composite "burning rate" chart they are listed 86, 87, and 88 respectively.
All are single-base extruded form. All produce on the order of 50 ft.-lb. per grain weight (E/gr.) energy (average). However, the bulk density of XMR 4350 and H4350 is 224 gr./cu. in., where IMR 4350 is 234 gr./cu. in. This makes a difference in load density.

For your 8 mm Mauser (I'm assuming that it's 8 x 57), the case volume available for gunpowder is about 0.229 cu. in. (a calculated value) with a 150 gr. bullet seated to SAAMI OAL. This equates to 51 gr. of H4350 or XMR 4350 for 100% Fill, and 54 gr. of IMR 4350 for 100% Fill.

But, given that the E/gr. is the same for all three gunpowders, you would want to back-off the IMR 4350 loading to 51 gr. also to get the same muzzle energy and velocity (and ostensibly the same pressure) as you would with the other two gunpowders.

I have to assume at this point that IMR is more than just a little bit cautious (or perhaps incorrect) in their listing. You will find that is not unusual when comparing the load recommendations from various sources.

Good shooting.

Robert

Try using a magnum primer with the big stick powders. Won't hurt, just start low and work up, with the extra flame and intensity it could get rid of the chunks.

Thanks guys. My Lee manual also lists 43grs of the IMR4350 as MAX. They must use data from IMR for their book which means they aren't testing those loads themselves. Strange. I'll work up loads with the IMR slowly.

Take a look into one of the cases after you charge it. There is a big difference in 43 and 54 grains. If it looks unusually low in the case (i.e. only 3/4 full), I'd suspect a mistake somewhere.

Save yourself some grief and use H414 with all loads in the 8x57 and 7x57, it's the only powder..Work up max loads with a mic.

------------------
Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Thunderbolt
I use 53gr of IMR 4350 and a 175gr Sierra bullet and CCI BR2 Primer in my 8mm Mauser and this not a MAX LOAD. I would have to agree with Ray on H414 I use this with my 200gr & 220gr bullet and it works great