I DID sight in my rifle before deer season, and I HAVE found that rifles shoot to different places depending upon the manner of support. I have read others say that rifles shoot to different places -- specifically they shoot high --if shot off of a hard support, such as a cement bench. These writers recommend placing some soft buffer material, such as a rolled up jacket, between the hard support and the rifle.

I shot a five shot 1.25" group (1" group choosing the best four shots)that was 2" high and centered left-to-right at 100 yards with my .243 at the range two weeks before deer season. I treat my rifles very gingerly and am confident the sighting was not knocked out of wack. Anyway, I should have sighted in from the sitting position rather than just off the bench, since I had noticed this discrepancy in the past. And certainly I think I got impatient and hurried my shot, which I kick myself for now.