Accuracy

[ssgross]

I've had a similar issue shooting AR with irons at an SR-1 black circle at 100yds. Indoors, it's easy to lose the front sight post in the "blip" of black when using a center or bottom hold. Staying on the rifle, and on the sights for 3 straight shots results in center, high, low pattern - cursing for not getting the group I want, then center high low again, more cursing than repeat.
The pattern would be different depending on how I would "drop in" to my sight picture. From the bench, I typically start under the target, then bring the front sight up. So the second shot I would come up through the target too much, and overcompensate on the third shot.
Even if I come off the sights between shots, indoors it's still way to easy to lose the front sight on a black background - and variation in sight picture is much less noticeable and harder to detect with the same precision as outside. First part of the solution is to come off the sights between every shot. Next part, I either print off red SR-1 bulls on white paper, use a "sliver of white" hold just below the bull, or use Jim Owens' trick (in one of his books) of painting a hairs-breadth white line in the middle of the front sight post, when shooting at my indoor range. I won't say how many rounds or range days it took me to figure out this silly thing. I would shoot great outside on the weekend, then go indoors on a weeknight - same rifle, same ammo, but crazy inconsistent results.

This may be wholly unrelated to OP's issue as he says he waited for the barrel to cool down between each shot, unless he sat on the sights the whole time - in which case I apologize for wasting these few bytes of space on the internet with my irrelevant observation.