I own 6 AR15, plus 2 more uppers. all are 223 except one. In the 223's I have one 1/10, two 1/9 and four in 1/8 twist. For most varminting I use 26gr Var, 55gr Vmax, rem brass because I get alot of it free, Win primers, trim on a cheap Lee spindle, finish case prep on a RCBS case prep center and load on a Hornady progressive. I weigh one charge out of about every 100 to 150 loads.
The FL length, Small base RCBS Dies are all I use so I know the ammo will work in every rifle I have. I shoot 5 round groups and the best rifle will shoot under a half MOA and the worst about triple that.
It won't win a benchrest match but if I miss a coyote at 600 and less, it wont be the gun or the ammo's fault.
Also I discourage 68, 69 or 75 gr match ammo on coyotes. It will hit them and kill them but they are not DRT and you may not find them. The plastic tipped Vmax or Amax will work much better, but the 75 gr Amax is too long for your AR mag. You can cut out the front of the mag and gain about 1/10 inch but they still do not feed quite like they should.
That my experience with Varget. Only improvement I suggest to Hodgdon is make short cut version that will meter better for progeressive presses.
I have been researching this subject on various forums for the last couple of weeks the sumation is for the 68 gr hornady BTHP or 69 gr sierra SMK use 24-25 grains of varget or R15. I have loaded the hornady's in varget and R-15 in 24, 24.3, 24.6, 24.9grs. Hopefully I can get to the range this week and will post results afterwards. I will be shooting out a 20" H-BAR RRA coyote rifle.