27 February 2015
The Lee 300 AAC mold is made on Lee's new mold block design with the round locator pins and very well made. Even with my many decades casting experience, the mold was not easy to get started for me. The bullets are very long, so mold temperature and pot temp needed to be a bit hotter than I expected to get good fill out.
I suggest you cast hot enough so that you get a velvety or slightly frosted appearance to your bullets. If you cast shiny bullets with this mold, the fill out will be incomplete and diameter will also be low.
I have cast this bullet in Lyman #2 alloy and also in 2% antimonial lead from jacketed pistol scrap. Both alloys worked fine but took very different temperatures. For me, this worked out to 725 F. for the #2 alloy and 750 F. for the antimonial alloy. I cast fast enough to drop bullets 3 times a minute. I use an outboard PID for pot temperature control.
I tried both alloys subsonic in 7.62X39 and I tried the harder #2 alloy at 2,000 fps in 30-06. bullets were size throat diameter for each application. The only surprise was that, personally, I got the best accuracy with the #2 alloy subsonic, 975 fps using H TiteGroup and no gas check in 7.62X39. I get consistent 5 shot groups less than 1/2 ” at 50 yards with the subsonic load and murdered several squirrels with the load from my Remington Spartan single shot 7.62X39.