70g Noslers are a better coyote bullet than a 70g sierra blitz kings, as they are tougher and less apt to explode on a shoulder. Imr 4350 and IMR 4064 have performed very, very well in 70g weights.
80g Sierra blitz bt are fabulous with a hot load of IMR 4064. If you like a heavier bullet, the 87g V max and Hornady 87g bthp with approx 37g of IMR 4064 both will be very accurate and deadly on coyotes. A close to max load of R#19 also works well with the 87's and 85g barnes tripple shock for deer.
Jay, I can not imagine what you are referring to in your statement, "In .243 I’d recommend staying away from any flat base bullets. So long as you do that you shouldn’t have any issues."
