I "think" the 17 Hornady Hornet would be good for fox also.
Otherwise, my plan is 55 gr FMJBT in the 5.56 at not over 3,000 mv.
I may get a runner sometimes but with the 1 in 7 twist my hope is straight line penetration.
I've read 17s are a good fur saver cartridge for fox, and believe a guy could find a bullet that wouldn't exit.
I'll share my .222 Rem experiences on Michigan red fox. They weighed around 12-14lbs. Unlike the 25lb porkers running the beaches on Kodiak Island.
I shot a number of 50-53 gr bullets in the 3,100fps range. All would blow out a minimum tennis ball exit on the far side. Some close to softball sized exits.
I shot a number with a Sierra 52 or 53 gr match bullet. Can't recall for certain as this was 45-50yrs ago. At the time I didn't think they would expand. I slowed them down to around 2,800fps. Same result on broadside shots. Baseball to softball sized exits. I got pretty good hand sewing them back together prior to sale. We'd get $60 - $65 per hide, which was nice for a teenager back in the late 60s to mid 70s.
Perhaps those Sierras were expanding? I was just a kid. I don't recall seeing shrapnel while skinning the fox. My belief at the time was the velocity alone, even with a FMJ .224 bullet hitting them at 2,500+ fps would cause blowouts on the far side. Just not enough substance to a fox to absorb the hydraulic pressure wave.
We shot quite a few fox with the .22 WMRs. 40gr JHP WW rounds were a perfect combo for killing the out to 120yds. Very little fur damage with those bullets at 1925fps MV. But too hard to guess holdover for good hits past 120-125yds.
Which is why I moved up to the .222 Rem. And learned how to sew!
About 1yr ago I decided to develop some reduced power fox fur loads for my AR15. A 9-twist 16" barrel. I purchased 2 boxes of Nosler Varmageddon bullets. 40gr and 55gr. I tried a few different powders and settled on H4895 as the best. I wanted a MV in the 2,100-2,200fps range. The 55gr loads will cycle my AR in semi-auto mode. The 40gr bullet turns it into a single shot. Have to work the bolt carrier manually for each shot.
BUT - I've not shot a fox with either load. There aren't any fox on the Kenai Peninsula where I live, and I haven't got down to Kodiak after fox.
If you think you'd like to try these reduced .223 Rem loads, PM me and I can share my load data via e-mail or text message attachment. The loads should also be equally good with Hornady V-Max bullets of same weights. I was just looking for the most frangible bullets available. The 40gr would likely be the better fur bullet on 12-14lb fox.