A friend of mine picked up a '70s LH 700 BDL in 25-06 that had a very crppy scope mounted on it. We were at the range one day shooting some guns and he offered me a chance to shoot it. Moving over to the bench he was firing on he had a 4"×4" with a straight sandbag on top under the forearm. I got behind the gun and put five shots into a sub ½ moa group at 100 yards shooting Remington Core-Loks. Last time I talked to him no one has been able to duplicate the group, honestly I doubt I could do it again myself.
We had a Factory Class at our club benchrest matches. Ole Mr. Wright was pretty strict on the rules governing what constituted a factory gun. The rifle had to have a factory barrel, stock and trigger, no forearm adapters or lead sleds allowed. I shot a 700VS in .223rem that would agg in the mid .3s, I got my a$$ handed to me by a very good shooting Cooper in 6ppc.
If doing load testing I prefer to use the most stable rest setup available...