I think what happens in that you induce a different harmonic to the barrel and or the rest. Now sitting with arms rested between the knees, you bet my favorite position, IF, the terrain allows. Sometimes though the grass is a bit high to see or shoot through.
No matter what the position though, you need to practice the same as you would be hunting. I normally shoot standing with a two hand hold out to 50yds. I shoot more at 25, but once I settle in and am shooting good there I move things on back. Most of my shots fall within this range, but I havbe had quite a few on hogs which were in the 50 through 100yd range. Once you can keep them in a 2-4" group at 50, usually they will hit within that area on out a bit if you have practiced a lot. My last hog taken with my 454 was at a trot at 87yds, and the big Lee bullet literally flipped the 150'ish pound sow rear over ears. It hit just in behind the onside shoulder and exited in the lower third of the shoulder on the off side, literally pulling the rug out from under her.
I am also not loading to top end velocities, I find something that is accurate is WAY more forgiving. With my 41, I am loading a 200gr Rem SJHP to only 1350fps. It is VERY accurate out to 100yds and will relaibly drop most of the hogs I shoot that far at with one shot. With my 454, I am loading the Lee 452-300 to only 1550fps. I have found this to shoot well into 1" at 25 and 50yds standing offhand as mentioned above. I have loaded it up to the 1700fps range, but neither the groups nor myself really liked that area.
If your loads are comfortable to shoot, and your accurate with them you will do good. Just remember to not introduce something into the plabn that hasn't been there before. Even resting my elbows across the hood of a truck has thrown my shot off high. I am guessiong that the solid hood under my elbows simply didn't recoil the same as when on a softer rest. Either way, the big ol hog just saundered on off into the woods.
