Armednfree,
I've been using the Caldwell The Rock Benchrest rifle rest, in combination with a Caldwell, rabbit-ear bag for the rear for a decade now. It's similar design (and weight) to some other heavy front rests, and have shot many 5-shot (not 3-shot) groups less than .2 inches off it using my 6mm PPC bench rifle, and a number around .15.
On the other hand, my everyday front rest is the standard Caldwell Rock, which is a basic tripod rest weighing less than 1/4 as much. Partly as an experiment, I used it with the 6mm PPC rifle last year when I forgot to take the "big rest" to the range. Was trying a new bullet and powder, so seated the bullets a little shy of the lands (usually seat them touching in this rifle) just to see what velocity/pressure was before proceeding further. Turned out all the groups had four shots in around .16, with one "flier" that opened them up a little.
Was that due to the lighter rest, or seating the bullets a little off the lands? Dunno, because testing conditions and my schedule haven't coincided since. The weather went from windy, dry and very warm(a new 70-degree local record for December in this part of Montana) to well below zero within two weeks.
But might have to compare groups off both rests this spring....
