Check this old thread from April - http://forums.nitroexpress.com/showflat....true#Post103063

I am repeating my post below.

....FWIW - here are some of my conclusions.

1 If the barrel is not free floated & the rifle is not bedded, the point of impact will change between shooting off hand , off a bench rest, a sticks or off a pack in the field or off your palm cushioning against a rock or a tree.
2 This change in point of impact varies from rifle to rifle. Some will change 3 or 4 inches & others just 0.5 inch. It used to drive nuts until I came to conclusion 1 above.
3 Point of impact will also change between a cold & hot barrel or a dirty & clean barrel - again each rifle is different & some change more than others.
4 Even with bedded & free floated rifles, the point of impact will change if you rest it on a hard surface like a bench rest or a log. The bounce at the time of detonating the primer seems to affect the barrel vibration & shots tend to go high.
5 The change in impact is minimised if the rifle is rested on the magazine just in front of the trigger guard & this hard rest is behind the cartridge / chamber & does not seem to affect impact change as much. If the fore-end is cushioned by the palm over the hard surface it also reduces variance in impact.
6 If you rest the barrel on a shooting stick, the point of impact will change all over the place as the barrel vibration nodes will not be the same for each shot. If you rest the fore-end on a shooting stick, make sure that the stick has a soft pad to absorb vibrations or rest your palm on the stick (if possible).

I would like to hear the views of others with more experience on the matter.