I have a 300 win mag and have 3 friends with the same. Also shot and used 3 or 4 .338 winchesters, a .458, and 2 .375s. Have hunted with a friend who carries a 7mm mag Rem 700. Don't ever recall a feeding problem at all let alone related to the belt. I've short stroked my 300 a couple times but that's operator error. Never have known of a problem among the guys at the range either - and here in AK there are a LOT of rifles in the 7mm to .338 mags as well as quite a number of .375 to 460 mags.
I think the "problems" may mostly be manufactured at a writer's desk or some early (50's-60's) poor conversions of '06 rifles. The guns mentioned above are mostly factory, several Winchesters pre 64 to mid 80's, 70's and 80's Rem 700's, 1 70's and 1 80's Sakos, one FN Mauser (60's??), and a Browning A bolt early version, 1 80s ? Colt Sauer.
I think all belted handloads are better off if they headspace on the shoulder.