Have found TAC to also sometimes respond better to magnum primers. It depends on the application. Any spherical powder can, though it's more common with slower powders. The burn rate in sphericals is not controlled by granule size, as it partly is in many extruded powders, because sphericals all have very small granules. Instead it's controlled by "coatings," which actually don't just coat the granules but infuse them them with a burn deterrent. (Many extruded powders feature such coatings these days, the reason we have smaller-granule, slow-burning extruded powders, such as the "short cuts.") This is why hotter primers tend to work better with spherical powders: They ignite the powder more consistently despite the deterrent coatings.
That said, it also depends on how much accuracy you want or "need." If you're hunting big game at "normal" ranges, say out to 300 yards, groups averaging 1-1/2 inches at 100 yards work fine. Thus the potential halving of group size with magnum primers is irrelevant.
But what I have found (and mentioned before here and there) is that the average handloading deer hunter is not just interested in actually killing deer, but how small his groups are compared to those of his handloader buddies. This is due to most handloading deer hunters spending far more time in their loading room and at the range than actually hunting. Thus the modern conviction that "half-minute" groups are necessary to kill a deer at 100 yards, much less 300.
But that's also why I write about how to handload for finer accuracy: That's what most readers want--along with higher velocity and a bunch of other stuff that also doesn't have all that much to do with killing deer, at least for 99% of us.
