H335 is antiquated stuff. If that's all you have, go for it. But it's dirty burning and temp sensitive. It worked fine when the choices available were limited, but far better powders exist today.
H335 seems especially popular on the Fire for use in the 223/223 AI for a couple big reasons. Steve Timm liked it in the 223 AI, and is a very influential poster here. Much of his work was done in the era before the better powders were available, and I suspect if he were to revisit the subject he would find the new powders better suited.
Another big reason H335 still sees a lot of play here is Big Stick. He makes a lot of noise about it, and I suppose H335 does work well in his locale, which sees very minimal temperature variations throughout the year (something like 34 degrees between average summer highs and average winter lows). In areas with wider temp swings (the same site where I found the Craig data shows around 81 degrees difference at my locale), changes in velocity and thus zero are likely to occur between the seasons. Lots of folks listen to Stick, take his word as gospel, and repeat it without really trying anything themselves.
Benchmark, Tac, and IMR 4166 are some of the best powders I've tried with 50-55 grain bullets in the 223 which showed good velocity with accuracy. In addition, Tac and 4166 have de-coppering agents.
Also, H335 smells weird when it goes off.
