Ok so the reported W-W 748 loads might be good for the winter. So if I develop a load in 60 degree heat and shoot it in 35 degree temps . MY POI will change ? That's no good I think I stick with Varget.
Please understand I was trying to figure how they could get that velocity with 748. I got the 52000 pressure from the link you posted and added 60000 for a maybe. I used my velocities I got with better powders and lighter bullets just to try and keep an open mind.
But
I do not reccomend WW748 powder for the 223! I think they're being optomistic or simply smoking crack to think those velocities are attainable and safe. Both Benchmark and TAC give higher velocity and are less tempature sensitive, throw in cleaner burning and it's no contest.
I try to work all my loads in at least 90 degree weather. The 60 gr NBT load might be fine in colder temps but as I said it was too hot. From my limited experience, all powders are temp sensitive to some degree. Work up a safe load in the hottest temps you can and you'll be safe any other time. Even Varget will shift impact some with 70 degrees difference.
