Rock River AR15 Varmint Model

[Splat Shot]

I am about to take the plunge on a Rock River AR15 HBAR A4 Varmint model and was wondering from those more experienced at ARs, should I get a 20" or 24" barrel?

Rifle will be used for punching paper at the range from 100-300 yards and prarie dogs. I know the 24" weighs a bit more but I don't intend on carrying it around so no big deal. I also might get a few more feet per second out of the longer barrel, but is that about it?

Also any comments on ammo you may have used out of one of these is also appreciated. Thanks, Splat.

 

[GLOCKT]

The Bushmaster version of the Varminter is set up on a 24" barrel.
The more the better,I believe we say.
I've set my configuration up on a 24" barrel platform.24" V-match on a stock Bushy lower.Soon to get a trigger job.
As far as ammo goes,I'm shooting 55gr South African surplus or 63gr Swiss surplus.No difference in the two I just have to adjust the steel sights raise the elevation on the rear sight 2 clicks at 100 meters when shooting the 55gr SA.
Have shot both within my expectations out to 300 yards,considering the quality of non-boattail ammo and slow trigger.