6 XC brass, look no further than Tubb brass, excellent at a great price.
243 Winchester gets around 1200 rounds of really fine accuracy, depending on the powder used. With H & IMR 4895, Varget, R#15, IMR 4064,1/4"-1/2" accuracy in the many factory Remingtons, Ruger 77's that I have shot out on dog towns, chucks, and coyotes. By 1200 rounds you can not touch the lands with any varmint bullet, thus accuracy is hanging around 3/4" at best to 1", and this is where a barrel may hang for a couple thousand more rounds. 1" groups is not what I call p. dog accuracy.
In the 80's through early 90's, it was common to shoot 600 rounds of centerfire on a bad day, and 1200+ of centerfire on a good day. We had to cool the barrels with water to keep the guns shooting, rotating 6 rifle barrels which would have otherwise never cooled. The 243 and 6 Rem with 85g Sierra bthp was our windy day calibers loaded with IMR 4064. Several times, I burned out 243 barrels in two days of shooting, and I shot the leade out of one new Douglas barrel in an afternoon in 243.
This type of high volume shooting lead to me having a barrel vise welded on the grill guard of my truck where I could change out barrels, and we ordered Hart barrels ten at a time.
AA2700 in the 243 and 6 Rem added to barrel life, Win 760 was a good second choice.
H335 in the 223, AI, 6 BR, 6 BRX, 6 Dasher will give unbelievable barrel life, you have to learn to adjust to the temp swing, and KEEP YOUR AMMO OUT OF THE SUN! We used H335, then AA2230 for 20+ years varminting, never a problem, but you do learn some common sense about not shooting top pressure loads and Keeping your ammo out in the Sun.
Today,I would run 65g V max in a 6 BRA and 6 BRX(or Dasher), then I would go 87g V max, 6 XC or 243, with AA2700, and for LONG range, the 243 AI with the 87g V max and AA2700. Hornady discontinued the 105 A Max, and I don't know if the new 103 eld is the equal or not in being explosive.
No fun in seeing dogs just fall over, go for the blow = bullet mass\speed