If there is one major flaw in the current poll, it's that 6.5-284 and .284 are included. These cases are 55mm long, some 4 mm longer than the .308, so I don't know if they will really fit into a standard magazine/platform size. I only included them because that one custom maker of AR10 showed .284 Win on the website. But if they are possible, you'd probably have to load the bullets kinda short, not to mention turn the mag into single stack - but talk about some real performance! The reality though, is that a lot of case capacity is going to be compromised once you shove those bullets down deeply enough. But, OTOH, there is a LOT of case capacity to go around with .284 based cartridges!
.450 Marlin however, makes sense, as it's a 53mm case, and loads short stubby bullets. Sounds quite doable, if the bolt thrust can be handled.