Thread: Ecinomical load development in a component drought.

Greetings All,
Powder burning speed varies from lot to lot of the same powder. Sometimes this is minor but not always. I almost got caught out by a big change in the speed of AR2209 a few years ago and have pondered about it ever since. One of the things I learnt is that you need to check the speed of every lot of powder you get. The good news is that you don't have to go through the whole load development process again.
My current process is to load a couple of rounds two grains under my previous load and chronograph it together with my old loads. If the velocity is much the same then all is good. If not then an adjustment of the load is needed to achieve the same pressure and velocity. I find it easier to use a graph like the one below.

The rifle is a 6.5x55 Tikka T3. Also included is data for my M38. Load data for the 6.5x55 is patchy and conservative so I had calculated what should be possible based on case capacity. I also plotted the data for AR2209 and AR2213SC from Hodgdon and Nosler. As you can see the old lots of AR2209 are like the Hodgdon data and the Nosler loads are in line with the new AR2209. The plotted lines of powder charge and velocity are quite straight and parallel to each other. If you have your old load plotted like the Hodgdon data and your new load produces more velocity then you can use the graph to estimate the powder charge correction needed.
I have often wondered why the powder speed changed. First I thought that this could have been when ADI became the supplier of H4350 about 1992. Checking published load data for H4350 prior to 1992 shows no significant difference so we can scratch that one. My old tin of AR2209 stamped 1998 is the slow stuff. I turned up a post from a handloader in the US reporting the change in 2002 so around 2000 is a likely date. The why is a different matter and frankly I don't know. This change is not limited to one can or lot as published data from Handloader in 2007 matches my results for my current can purchased in 2019.
I use these graphs more and more. A few chronographed mid loads tells us where we are and a likely charge to develop maximum velocity. Saves a truckload of components.
Regards Grandpamac.