Bake,
If you are talking about down pressure on the barrel when you wrap your arm in the sling, then yes, that can and will affect the point of impact. The tighter you pull, the more tha shot will be off. The solution to this problem is to sight in over the bench, then try the gun/sling combination shooting offhand, and see how much it throws your shots off. You may then wish to adjust the sights so that they make up for this extra pressure. At the very least, you will know how much it throws the bullets off at measured distances. Welcome to the group, by the way. Hope you have fun and learn some new things here. Bob H.