Tank1949,
The only temperature-stabilized spherical propellant on the market is the new Winchester StaBall 6.5, which is a little slow for the 5.56. It is intended for the 6.5 Creedmoor, which has a smaller expansion ratio cartridge than 223 in a standard 24" pressure and velocity test barrel. That gives a slow powder more time to reach peak pressure before expansion causes pressure to drop.
In stick powders, temperature sensitivity is controlled by manipulating the deterrent coatings. This is made possible by the fact progressivity of the burn can be independently adjusted by the grain geomethery (grain size and the number and size and configuration of perforations in it). With spherical powders, progressivity is controlled entirely by how the deterrent coating concentration falls off as the grains burn from the outside inward. There is no equivalent to a perforation to control progressivity independently of the deterrent control. For that reason, the Western Powders site FAQ says spherical powders cannot be made temperature insensitive. So, what has General Dynamics done to make the StaBall 6.5 parent powder temperature insensitive? I have no idea. They've pulled off quite a hat trick there. I don't doubt they developed it for the military because of the scheduled deployment of the 6.5 CM for snipers this year (as well as for a number of other military arms as their new medium power cartridge). Winchester or Hodgdon (Winchester's distributor) was smart enough to get it made in canister grade for handloaders. I expect it will prove popular. I have no idea whether GD will eventually develop a parallel product for the 5.56 or not.
For stick powders, the Hodgdon Extreme line and the new IMR Enduron powders are the main choices available for temperture stability. Alliant Reloader 15 claims stability, but the military had some issues with it in desert temperatures and good old IMR4064 did better. The newer Reloader 16, though, claims "world class" temperature stability, so it is probably a better bet from that company's line.
All the non-compensated powders can be compensated for approximately by the formula built into QuickLOAD as to temperature effect.
Be aware that temperature compensation in powders depends on them being in a cartridge that produces a certain range of pressure and rate of pressure rise and those are affected by case capacity and bullet weight. Varget, for example, seems to do pretty well in many .308 Winchester loads, but in .223 Rem most folks say they can't tell it from any other powder.
This article is informative.
As to not being able to dispense stick powder volumetrically, this is misleading and also untrue if you have the right measure.
The JDS Quick Measure is guaranteed to keep them within ±0.2 grains and often does better. I've been using one for several years now, and can confirm that performance. A second factor is that stick powders burn more slowly when the grains are packed closer together because the ignition flame front has a harder time moving through the resulting tighter spaces between the grains. For this reason, the right stick powder, when the measure throws it heavy, can impart the same velocity to the bullet as a lighter charge of the same volume. Like temperature compensation, how well this works depends on matching the right stick powder to your cartridge and bullet combination for best effect. When I pulled down a box of Federal GM308M, I found the IMR4064 inside had a 0.4-grain weight span. Board member Statshooter did the same and found a 0.6-grain span. It shoots just fine.
Finally, why weight over volume? Weight is a more precise measure of the amount of chemical potential energy being dispensed into a case if the powder is kept and dispensed in reasonably stable relative humidity. If the humidity changes from low to high, the weight of the powder increases up to 1.5%, so your scale can under-measure potential energy by that much in humid conditions. But the volume of the grains doesn't change with that added water content (it doesn't swell) so a carefully used volumetric measure can actually dispense energy content more accurately under that circumstance. But then there is another problem. As the Norma manual says, powder burn rate can increase by 12% going from 80% RH to near 0% RH. So even if you keep the energy dispensed the same, powder that gets too dry can take you right out of a load sweet spot. The bottom line is to keep your RH constant at about where the powder makers keep their stocks because that's the RH that their load data will have been developed with. 60% is a good compromise between what the various distributors report having. Norma also points out that water molecules are small enough to slip past primers and bullets in unsealed cases. If you change the RH you store your cartridges in, expect the powder to gradually start reflecting that change over a period of about a year, at which point it will behave as if the powder had been stored in that new RH all along. For this reason, you never want to desiccate loaded cartridges in storage and you don't want to desiccate your powder unless you don't mind published load data for it becoming invalid.