Re: Barrel length
As mentioned, a shorter barrel shouldn't prevent you from shooting to 500-700 yd with no problem. Compared to the 28" barrel, you might expect to lose somewhere in the neighborhood of 150 fps muzzle velocity, maybe a tad more (~15-25 fps per inch barrel length). However, at those ranges, you'll just have to dial in a little more elevation on your scope to compensate for the slower MV. You should be quite a way away (distance-wise) from a range that would be beyond the capability of the 20" barrel, as long as you optic has sufficient travel to allow you to dial in the necessary elevation adjustment.
