We've shot a couple hundred 123s outta the .260s with IMR4064 lately. Somewhere in the 37-40 grain range has been good in a couple rifles now. I've shot them below freezing and shot some yesterday when it was 95 without any noticeable shift in POI. IMR4064 is available everywhere.
I also have found IMR4350 pretty much everywhere. I have not found it to be nearly as 'temp sensitive' as most would imply.... funny how those old wives tales seem to propagate.
