H335 is always a classic powder with 50's in the .223. In fact, in the 1990's it was pretty much the universal choice. Guys would ask, "How much you using?" and it was understood they were talking about 335.
I would guess your powder isn't more than 20 years old? That's about when Hodgdon ran out of the original mil-surp powder and started having H335 produced for them. The earlier powder was a little slower, and many shooters used up to 28 grains. Today Hodgdon's listed maximum is 26.0 grains, which normally shoots very well.
