Varget is Ar2208. This is one of the Australian Rifle series made by Australian Defence Industries.
All the Ar series are temp stable. Ar2207 = H4198, Ar2219 =H4198, BM2 = Benchmark, Bench Mark 8208 = 8208 XBR, Ae2206H = H4895, Ar2208 = Varget, Ar2209 = H4350, Ar2213SC = H4831SC, Ar2217 = H1000, Ar2225 = Retumbo and Ar2218 = H50BMG.
I work up in the hottest temp at home about 80ish*F using Federal Gold medal match, quite a soft primer. My hunting temps are 95*F to 105*F in out back Australia.
I look for the best group and stop when either the velocity (magnetospeed) doesn't go up any more, the primer flattens out or I get mild cratering. Remember soft primers.
If I get hard bolt lift before my desired velocity I change powder.
This procedure has worked well with all the above listed powders.
This procedure does NOT work with the double based powders I have used these being
Win748, Win760, RL15, RL17 and RL22. RL17 & 22 I will no longer use due to their very rapid over pressure in the last grain or so near maximum.
Now I work up any double based powder actually on the property.
Steve, work up in the maximum temp. you have at home and you should be good for 20* more in your hunting area.
Note well - I am using soft primers.
Steve.