For prairie dogs, I've been loading 39 grain Sierra Blitzkings and 40 grain Hornady V-max bullets with CFE223 powder and Remington 7-1/2 primers.
My rifles also shoot the 32 grain bullets well, I use mostly 32 grain V-max.
The heavier bullets do a bit better, flatter trajectory and more retained velocity, out to 500-600 yards than the lighter bullets.
My rifles are a Savage 12FCV and an AR-15 with a 26" heavy barrel.