You can e-mail Marty on the 458 SOCOM forum site. The forum has been down for some time but he'll answer you eventually. I believe there is also data posted on AR15.com. I'm still working on loads for mine. The best I've gotten is about 1 inch at 50 yards for 3 shot groups; I'm hoping for 1.5 inch 100 yard 3 shot groups but haven't gotten there yet.