I've used the same load for many years and haven't found anything that shoots better in the various .223's I've shot it through.
I've never found it (BLC2) to be particularily temp sensitive. My only observation is that if you are hunting/shooting where the ammo/gun will see temps below 0degF, or above 110deg, you might see some issues.
For cold temps, you'll likely need a magnum primer. For high temps, you'll need to drop back to 26.0-26.5. I've found that at under 26.5gr w/55gr that accuracy starts to drop off.
I've tried several different lot#'s of H335 and have never found it to be more accurate than BLC2. It's not "bad", but just not quite as good.
Neither is it as "flexible' as BLC2 for other cartridges.
I've got an excellent 7mm08 load with 139gr Hornady BT's, and in my .338/06 and bullets lighter than 225gr, it's superior to everthing else I've shot through it.
It's also the most accurate powder I've found for my .35Rem, and is hands-down the most accurate cast bullet powder in the .35 (38.5gr for ~1,920fps).
A former co-worker frequently shoots prararie dogs and carry's his ammo in one of the soft insulated coolers with a frozen "cold pack" he got from his wife that's a nurse and are used to keep medications 'cool' when transported in vehicles by home-health nurses.
He was shooting p-dogs one day and rifle and ammo got so hot, the bolt locked up on a fired round. He also on that hunt shot out the barrel of a .22-250 in about 500rds.
He know's better now !!! And has gone to a match-heavy bbl .223 AR for the "extended" shoots. And he swaps guns after a 30rd magazine.
The only powder I've found to be perhaps less temp sensitive in .223 is RL15, but I only use it in loads with bullets 60gr or heavier.
