Originally Posted by Iclimb
Can powders of similar burn rates be substituted? My book only list ramshot Magnum was wanting to use something else. I.e can I take 10% out and start working up?
The answer is yes. I will always try to research data as much as possible but there is very little to no data in a lot of combinations. Newer powders such as RL17 and now RL33 have very little published data to go by and in the case of 33 I don't know of any.
I know that RL17's burn rate is very close to to H4350 which is a popular powder with lots of data and online recipes so when I started experimenting with it in different chamberings i looked for the H4350 data and recipes as a guide and started at about 10% lower than the max loads listed. The result were very predictable. With RL33, I know that it is very close to H870. I also know it's slower than Retumbo so the same charge of 33 for a Retumbo max load should produce lower pressure. To be safe I'll back off a little on that.
You don't want to back off too far. An extremely low charge can be trouble too.