I use H335 and have had no trouble with either 9-inch twist ARs or my CZ bolt gun, which I believe is a 12-inch twist. I just happened to chronograph my 60-gr load (using Hornady bullets) in the CZ last weekend, and was pleased with the results - right at 3000 FPS and a decent extreme spread over five rounds. Unfortunately I don't have the data handy. I gather there are more modern powders (like Varget) but have always had good results with H335.