It's been several years since I've used 2000MR in my .308. Yes, I got good velocity and found a couple good loads, but I stopped as I was not getting the consistency I look for due to wide range of temperatures I shoot in here in AZ.
I don't live in Arizona, but spent a summer in Tuson.It's been several years since I've used 2000MR in my .308. Yes, I got good velocity and found a couple good loads, but I stopped as I was not getting the consistency I look for due to wide range of temperatures I shoot in here in AZ.
I've also got some RL17 that I've used for 185 Jugs that also would perform quite well, but had the same kind of problem with temp sensitivity.
A few things
I think one has to keep in mind the objective behind the development of the hybrid cases . . . that being for short barrel lightweight guns to deliver the energy on the target that larger guns can produce.
Summer time in the Phoenix area, low temperatures often don't fall below 90°F (elevation here between 800 to 1700 feet, and Density Altitude around 150 to 400 ft.). Getting out in early morning to shoot in 90° and the temperature moves up from there quickly. Other times of the year, in a single morning is can easily move from 65° to 90°. The higher temperatures really slows down the rate of fire when target shooting.
So temperature sensitivity never bothered me here. It's a none issue.
The temperature won't change 20° by the time I load them to the time I shoot them most days.
And temperature is adjustable here 10,000 ft elevation just 60 miles away...in 30 miles the temperature usually drops 10 to 12 degrees in the summer. So I don't shoot in 90 plus temperatures. And always shoot in a stand of trees shaded and comfortable.
I shoot mostly in a 30 degree span summer to winter, 55 to 85 degrees, and don't go in extreme temperature conditions which are rare.
Traveling to hunt can be end up at 7,000 - 8000 ft. in much cooler conditions, which can make it a little challenging to develop a really good load at ranges in the Phoenix area before heading out.It's 56° here and won't change 10 degrees in 8 hours. I'd need a jacket if I head into the mountains to shoot.Summer time in the Phoenix area, low temperatures often don't fall below 90°F (elevation here between 800 to 1700 feet, and Density Altitude around 150 to 400 ft.). Getting out in early morning to shoot in 90° and the temperature moves up from there quickly. Other times of the year, in a single morning is can easily move from 65° to 90°. The higher temperatures really slows down the rate of fire when target shooting.
Thanks for the thoughts . . . some good ideas there! I've always been a fan of, what I'd call "real hunting", like taking game down inside 200 yds. And like you, I've always used jacketed lead . . .has always been my preference. Because of my age (78) and some physical limitation these days, I'm not trampling around mountains hunting any more . . . though I might consider less active hunting if a youngster invites me to straggle along and go after and haul any kill of mine.It's 56° here and won't change 10 degrees in 8 hours. I'd need a jacket if I head into the mountains to shoot.
Ya need to move up to the Canyon area, the part of Arizona that looks like home to me.
You are where you are and it does get hot.
Your lower elevation shooting numbers 1700 ft will be no good at 7000 ft...but Kestrel can help with that, for many.
I never used it hunting big game, just sight in for 100 yds. Or use the point blank method if expecting a long shot.
Never needed any of that cause the elk stay off the meadows and run the deep pole thickets several canyons in. Shots will be from 35 to 100 yds...mostly 35 yds and on the run or one good leap and they dissappear. Let them run, stop, wait, and track them down again, and kill them. Wherever they go you go.
I lived there for awhile in a log cabin with a tin roof, in the Blue Mountains along Onion Creek on a 4 wheel drive trail, working gold claim security for a mining operation.
Back to your template problem. You'll probably have to compromise, and see if a moderately temp stable will fit your needs.
What game bullet do you plan on using? Some places copper bullets are required, I always used jacketed lead.
Whatever the bullet it should be readily available and cheap enough so you can afford lots of practice.
What powders do you have available? And are they stable enough. H4895, RL 15.5?, Winchester Staball series, Varget, H4350, or IMR 4451 Enduron series pretty slow. Can enough be put in the case to reach s descent velocity in a hybrid case?
Cartridge overall length? Water capacity?
And ya come up with an answer as to which of the less temp sensitive powders are usable...not many.
One bullet and one powder for everything you intend to kill. That will build confidence, when you practice with it all the time, any temprature,
Take your 308 small game hunting alot. Shoot squirrels & rabbits running and standing, with your big game load. Use various field shooting positions.
I only mentioned the hunting issue as I often find myself helping some hunters around here at the ranges as the hunting season starts. Instead of going out and shooting squirrels and rabbits with my .308, I'll shoot flies. 
