For .375 H&H are these two powders interchangeable, grain for grain ? Thanks in advance for all replies.

I ran across this on another talk forums
copied::
I ran into this several years ago. I had always been on the lookout for Norma powders but could never find them locally. I was reading through one of my reloading manuals (A-Square) and came across a section advising to never substitute powders for another brand. The manual listed three exceptions, RL-22 is the exact same as Norma MRP, RL-19 is exactly the same as Norma 204 and RL-15 is exactly the same as Norma-203. It went on to state that these powders are all made at the same plant at the same time. They are only packaged in different containers for marketing.

I personally called Alliant Powders and they confirmed this information. I will say that this was several years ago (probably 8 or 10) so you might want to again verify. I do know however that some Alliant powders are still made in Sweden.

I have used both powders. I believe they are almost the same. But I still work up new data just because of changes from lot to lot and Murphy's law is usually in my pocket.
I haven't seen any reason to pick one brand over the other , except for price and availability.

Vines, I read your post multiple times.
I believe it needs a little clarification.

It is my understanding and belief that RL 15 is the same powder as Norma 203B----
NOT Norma 203.
I've also read varying thoughts/theories on RL 15/Norma 203 B temperature sensitivity/insensitivity.
I would/do make sure I'm loading from the SAME lots !

Although possibly quite similar, it is wise not to consider differently marked powders the exact same. Different lots of the same marked powders can be quite different. Always caution.

Folks,
Thankyou very much for the replies above which seem to give the info I was hoping for. RL15 is my preferred .375 H&H fuel which seems unobtainable here ( again ! ) so looking for the best substitute. Others like Varget or IMR 4064 are OK but overall RL 15 ticks more boxes. It seems Norma 203B would be the go to choice. And yes, all cautions noted, my usual approach is to start low and work up carefully. Just common sense, and I like sensible !
Cheers

Same in Germany. R15 nearly impossible to get but 203 B is available. To be prudent I start low but 203B is a top powder for 375.

According to the late Don Heath of Norma, RL-15 is just another batch of Norma 203B. Norma uses it at the factory and also sells it to Alliant who repackages it and sells it as RL-15. You will find more consistency batch to batch with Norma 203B.

R 15 is the same as N 203B is the same as Rottweil R 903 (all made by Bofors, Sweden)

Alliant RL-17 / Reload Swiss RS 60 is IMHO better powder for .375 H&H

Jiri

Jiri,
IIRC you posted before about your preference for RL17 in .375 H&H. I actually tried it as well. For me I think fps exceeded RL15, but that was all. I definitely preferred my results with RL15. Better accuracy and more POI consistency with different 300 gn. projectiles.

However, would love to be able to buy RL 17 for my 30.06, but just nothing to be had here currently

I had a lot of loads with R15. As basically nothing from Alliant is shipped to Germany these days (which is a pity) I tried 203 B. If not identical then very close. And we can get it here.