Originally Posted by pasky2112
I'm glad to see you have been using Blue Dot for so long. I just purchased a new G20 and reloading/handloading componants. I chose Blue Dot and Starline brass. But I'm not sure if i should go with CCI 300's or 350's. What is the logic of choosing a mag primer over a std primer?... slower powder = mag primer?
Go with 300s. There is nothing about 10mm auto that requires mag primers. I do use 350s for a couple of my pet loads with Accurate no. 9 (A9). A9 is about the slowest-burning powder suitable for 10mm Auto. It doesn't necessarily need
mag primers. I did workups with mag primers years ago and I have loads that work great. Standard primers would probably work fine too. I just have not fiddled with re-tests since I have loads that work very well.
Bottom line is that mag primers can alter the burn speed of powders and impact presure in an undesirable way. All of the powder manufacturers that I know of call for standard primers (or in-between Winchester LP) for 10mm. Speer calls for mag primers for certain powders, but they are a rare exception in the various 10mm manufacturer data.