At what temperture do powders start to deviate? I shot some of my .223 reloads with W748 27.5 grns/450 primer yesterday and the group opened up by 1" at 100yds. Same reloads two weeks ago shot .5 at 100yds and the temp was 70 yesterday and maybe 52-55 two weeks ago. H.H.

All powders are different as far as how temp effects them. Typically, the ball powders are more sensitive than others. I had to change the powder in my 22-250 for the same reason. I was shooting H380, which gave me great groups at 40-50 degrees, but opened up considerably above that. I switched to IMR4895 which seems to handle the temp ranges much better and still produces great groups. Never tried them, but I hear the Hodgdon Extreme powders do very well over a very wide range of temps.

ADI powders are reputed to be very stable and now Hodgson are using some.

Hodgdon powders that have the small label "EXTREME" on them are very temperature insensitive. I may stand corrected, but I believe that their testing a few short years ago indicated that the variation in velocity was eight'/sec from 125 down to zero degrees Fahenheit. Their ball powders are not included in this catagory, only their extruded powders. Mike

Most of the ball type powders are sensitive to temps, more so than the extruded types. If you want a more stable powder then consider the Hodgodon Extreme line or the Ramshot powders from Montana. MtnHtr