I swear by Rock River Arms 20 in. Varmint Model with the 1:8 Twist.
I have my second one since one of my friends had to have my first one. They both will shoot 1/4 MOA Groups at 100 yards. That is from the bags and when I am having a good day with good ammunition. A couple of times I was using Federal P223E 55gr Boat Tail Hollow Point. Cant beat the two stage NM trigger that comes standard and also the standard winter trigger guard for cold weather coyote hunting while you are wearing gloves. And they do not cost you an arm and a leg!
Not really. The barrel length does not have that much to do with shooting heavier bullets. Regarding the 20" and 24" It is the barrel twist that dictates what you need to stabilize the heavier bullets. The 1:8 is just fine for most all grain bullets. The 24" barrel is OK for shooting stationary positions. But front heavy for carrying around if you do much moving. The 20 Bull Barrel Varmint is about all you want to handle if moving and then it can be a chore as the day goes on. And shots up to 600 yards.
Foe example the 1:12 Twist will not handle much over 55 grain bullets without loosing stability and giving some key holes. The 1:8 will handle up to 80 grain if you single load them in the chamber. So 60s and 70s bullets are fine.