For the sake of discussion and no I'm not being argumentative...
The belts on some case designs are from over a century ago when the H&H cases debuted in Africa. Holland designed the cases so they would slip in and out of the double rifles easily by using a very minor angle on the shoulder of the case. The angle was such that there was not a positive headspace. The belt was added for positive headspace. The rest is history including the term "belted magnum" as an indicator of strength and power...
Fast forward. Many shooters shift the headspace on belted magnums to the shoulder thereby eliminating the belt as any influence. There has also been an influx of beltless cases in larger capacities hitting the market.
300/338 Norma Mag
338 Lapua Mag
300 PRC
6.5 PRC (for the original Poster...)
others
Many of us can also turn the belts off of belted mags allowing the headspace to shift to the shoulder. A new HS gauge is required.
I personally have no gripe against belted cartridge since they make up a nice percentage of my work. But I also accept the newer crop of non-belted magnums as being suitable substitutes for the belted variety.