From the above posts I'm assuming that most comments are regarding factory barrels.
I'd like to start a discussion with Eddie, but I'm smarter than that, I'm pretty sure, well maybe.
I'd most probably learn enough to become even more dangerous.
I wonder if the rules change with a high intensity/extreme cartridge with a really fast twist. If they do I'd like to start a discussion with Derek M, about into the lands or not. Again I'm smarter than that. Though not much.;)
My experience with a cartridge that requires fire forming causes to agree with mikecr's last statement "I don't see how any conclusions can be drawn across the board though."
I as well as others notice a bit of a difference in accuracy when using the COW method of fire forming. The difference is evident between the first and second "real" shot. One has to look really hard to see it but it's there.
I've been using a stout load for fire forming to develop drop charts etc and use them for "rifle golf" and they are plenty good enough. Being anal though, I verify after the first use of the case.
After the second firing of the case there is no more fiddling just shootin'.