My experience with actually chronographing H335 and TAC loads in various temperatures, outdoors with the amma AND rifle at ambient temperature (as opposed to running them through a rifle attached to a Pressure Trace) is that H335 is indeed far more temperature sensitive, both to cold and heat. And I have had some of the same problems as Ingwe when using H335 on hot days when prairie dog shooting.
One factor with with the .223 AI (and in fact probably the major factor in velocity gains over the standard .223) is the SAAMI maximum average pressure for the .223 is only 55,000 PSI, which is reflected in published data. Normally traditional "pressure signs" don't show up until somewhere over 65,000 PSI, so handloaders working up loads in their .223 AI's are often loading to at least 10,000 PSI higher pressure.
