I saw a 41 fps change from 40* to 70* shooting 180-grain Partitions in the .30-06, fueled by Re17. That's not a tremendous velocity change (1.3 fps/deg), but what I didn't like was that it seemed to bump me out of an accuracy node. Went from 0.6" to over 2".

I hunted with a group of guys in Oregon who where all serious gun nuts and handloaders and they had several 6x47L and 6XC and they swore by Reloder 17. We were shooting LR Rockchucks and they certainly had those rifles dialed in. They scoffed at idea it was temp sensitive but they don't have to deal with Texas temps.

And what was the total charge weight in those cases?

I would say an educated guess would be 40-42gr with 105bullets

My results from rl17 are very similar to chads 1fps per ° in temp. So far varget, h4350 and imr4451 are all around .18-.20fps per ° in temp and rl16 seems to be there or a touch better.

Your last statement is probably the most telling fact - most people in Oregon don't even own air conditioners. The temp swings up there are nothing compared to what we see down here, especially assuming that they're probably not even out shooting in the coldest temperatures they see, whereas we are just as likely to be out shooting in our coldest or hottest temps.

I have done a lot of technical reading on powder temp stability and have spent many long phone calls with the guys who actually make the powder at St Marks (who make a lot of powder for Hodgdon and Alliant). I have a lot more technical knowledge on powders than most people do. I have to know these things to avoid pressure problems due to temps.

And it's not just the outside temp you have to worry about. If someone leaves their ammo box in a hot car, or in the sun on the table at the range for an hour or more, how hot do you think that ammo really is cooking in the sun? 140-160+ degrees. If you work up a max load at 40-50 degrees, and now that ammo is 140+ degrees, you just increased your speed by 100+ fps, and most likely are blowing primers and locking up your bolt, simply due to a powder that is temperature sensitive. I have to protect against that with better powders.

I see guys all the time shoot multiple rounds (get their barrel and chamber hot), and then close the bolt on a live round and wait to shoot. While you are waiting, that round is "cooking" in the chamber gaining in temp, which will certainly effect the pressures and speed. It's all these little things you have to think about and protect from. Or at least try to control it better.

Most double based powders are about 1 fps per degree, some more, some less. Your more temp stable powders, like Varget and H4350, run about .2 to .3 fps per degree. So, they are MUCH more stable, but are not immune to having variations due to temps. Some of the newer powders have been engineered to be much less temp sensitive, and they are. The new line of Alliant 2000 MR and 4000 MR are my little hidden jewels. They are more temp stable than Varget, and are slightly slower burning to get more velocity than Varget with the same pressures. These are great powders.

I have shot multiple calibers with testing R17. I have compared the velocities from cooler to warmer temps, as well as my customers who requested R17. I came to an easy conclusion that this powder is not for me to use due to it's high instability from cold to warm temps, and for other temp factors. I'm not saying it won't work. It obviously will. But is it a powder for me, no.

MOST of my customers do that. And I have to explain to them why not to do it. Cooking the cartridge, plus the fact that it's a loaded rifle they are moving.

^^^ Exactly. I see this all the time, also. You have to consider ALL factors that will cause temp issues.

Not looking for an argument, but seriously, is 1fps per degree really a factor with hunting ammo? I mean, 50-70fps is virtually meaningless at normal hunting ranges in which shots are taken.

Keep in mind I'm talking about the elementary practice of working up loads in temps approaching what you'll be hunting in.

Chad...that is good info on latest powders.

Is a simple velocity spread a big deal at normal hunting temps? No, not at all. You are exactly correct. But it could easily be a factor if a max load was worked up in the winter time, and that same load was being using in the summer to hunt pigs or coyotes. It could easily turn to a hot load or dangerous load in the summer. Then it would be a factor. So it depends on the load and how/when you are using it. It's always a consideration to plan for.

And another thing to think about, that 50-70 fps can easily take you out of an accuracy node. In normal factory rifles shooting 1" at 100, and getting out of your node and shooting maybe 1.5" to 2" at 100. Would it still kill an animal within 200 yards, yes. But if you have a competition rifle shooting .25" groups at 100, and you add the 50-70 fps, it can easily change up your groups and accuracy. It all depends on your set up. For precision loading for ultimate consistency in your ammo, it's a big factor to consider.

I still have ammo loaded with IMR 4350 in my personal 270 Win. Are there better powders that are less temp sensitive, yes. But IMR 4350 shoots so dang good already, why change. It's a Howa 1500 in 270 Win shooting about 3/4 moa, maybe a touch better. It's a tried and true load for me, and I still use it all the time. It won't matter for the distances I plan to shoot at with that rifle.