David, my long time working load for predators in that rifle has been the "old" Berger 25 Match at ~3900 fps. The load I worked up for the new Nagel 25's is ~3850 fps. These are pretty high velocities for the Mach IV. Sneaking up on .17 Rem. territory.
I haven't killed enough critters with the new Nagel 25's to form an opinion yet. So far, excellent on coyote fur and pops jackrabbits pretty good. But, very small sample at this point, really too early for me to say much of anything.
All the bobcat I've killed with this rifle were using the old Berger Match and never put much of a hole in any of them. That has really been my gold standard for saving fur - the old Berger Match at ~3900 fps in a 10T barrel. Just a consistently excellent fur combo on coyote and bobcat. I'm hoping to equal that with these new Nagel bullets. But only time and experience will tell.
Fox... I never target them, just every once in awhile one surprises me and shows up on a coyote stand. From my very small amount of experience, I would say the above combos probably are not going to be consistently fur friendly on fox. Probably pretty inconsistent, in fact. Great some of the time, much less than great other times.
The guys I know that kill and skin a lot of fox all seem to like the Hornet case. In both .22 and .17 flavors.
- DAA