It's been about 7-8 years since I had a belted mag, and I found that after about 3-4 loadings the brass couldn't be sized enough to get it to chamber in either gun. About the collet die you refered to, I read a piece in Precision Shooting that they were using it and it extened their brass usage to about 8-10 reloadings, and yes it is pricey. Back when I reloading for the .300 WM it was about $75.00 plus shipping for this die, I'm sure it's much higher now. The belts on the cases are a cheap fix for a poor case design, that spawned from the H&H cases. Back when these case were designed, almost no one reloaded so it wasn't an issue. Wilson make a die that is supposed to return the case to its original size, this might be the ticket for case sizing, instead of the collet die. The Wilson dies however, should be used with and arbor press.
those who beat their guns into plowshares, will plow for those who didn't