The H-870, or the powder I have AA 8700 (which I'm convinced is the exact same stuff), is so slow burning that I really do not think it's possible to overload it, especially not in a big straight walled case. I started using it with heavy jacketed bullets in 7mm mag and even as big as that case is and as over bore as it is, a compressed load showed no pressure signs at all, primers looked very nice and extraction smooth as glass.