It seems like brass these days has more concentric necks, and this doesn't seem to be as
needed as it was years ago. I think the brass manufacturers have fianlly figured out that
1) concentricity is important and 2) how to actually control it in their manufacturing process.
I have a Forster, and have used it, but most brass today is pretty darned consistent, plus
discussion with a friend who was a national champion benchrest shooter, and who made
his living making benchrest bullets for a decade let me know that this is usually not much
of a problem with normal chambers in normal guns. In benchrest guns with super tight
chambers, esp the necks, it can be important to thin the neck to get just enough clearance
to release, but still align the neck (bullet) very precisely with the bore.
Try it , esp if you have a bunch of old brass and a really accurate rifle. Never hurts, and it is
fun to learn.
Bill