well if the barrel is free floating you shoudlnt have to worry at all
if the barrel is not free floating you might have your point of impact a bit higher, this happens with my M4 Carbine if i rest the barrel on something
Yes poi will be different. If you are shooting off a sandbag in your hunting stand use the same support method when sighting it in. If you are going to hunt unsupported, then a sandbag rest is probabyt a better starting point for sight in. The bipod adds weight and will hop during recoil. I try to do my sight-in using the same support that I intend to use during the hunt, if ppossible. If not go for it and good luck
Yes. When you fire your gun, the barrel vibrates. This is taken into account, and is compensated for. So, when you touch your barrel to a solid surface, this will absorb some of the vibrations. A good example of this is an MSG-90. To compensate for the lighter barrel, they attach a weight to the barrel.
Thanks all, big help. As Jeff850 said my barrel is not free floated, so that might be a cause. As JeffVn said, I'll try to sight in using the support or position I will be firing the rifle from when hunting. I had zeroed at 100 m sitting, supported by a ruck sack, and when I took it back to 300 m bipod supported and prone, the groups were still tight, just in different positions. I'll just remember that if zeroed with the biopd, use the bipod. Of course, at shorter ranges the POI shift won't matter too much.