I found a bunch of H-5010 I have seen loads before for my 338-378 and have heard of 264 win mag loads.This powder is at least 10 years old in a store as new is it still good?I finally found some more H-870 which my 264 win mags love.Is h-5010 a ball powder?

It is excellent in the .50BMG with 600 grain bullets
H-5010 From 190.0 grains to 217.0 grains
IMI 50 BMG Primer

It is useful in the 6mm/284, .270/300 Weatherby, 7MM RUM, 7MM Rem. Mag., 7MM STW, .300 RUM, .30-378 Weatherby, .300 Winchester, and .338-378 Weatherby (but not my powder of choice).

If I am correct it is about the slowest burning powder around. Is this correct? If so, i would think you would need a pretty long barrel to take advantage of it(26"+)

I cant find any current data on this powder.The 338-378 loads I saw where at least 10 years old.I need data for 115or 160 gr bullets in a 264 win mag .The 338-378 I shoot 250 gr anf 300 gr Serria match Kings.