I've been having wompum good luck with H380 and 52 gr sieras for target,but now I'm diddling around with the notion of 4000+ FPS from 40 gr Vmax's. 41 grs of H380 will only make 3850 fps. I know its easier to get umpum from varget.I also know that it heats things up considerably more than 380. How much does all that extra heat translate into throat errosion?