You guys lack imagination. How many feet of dirt behind the dead animal is "enough penetration?" Why would we limit the Whelen to 250 grain bullets?
Is the argument really that there is zero effect by jumping up from 30 caliber to 35 caliber? If that is the argument, I'd argue that you are likely correct, given that 6.5mm non-expanding bullets have been used to kill all of the largest dangerous game animals on the planet many, many times.
The question then becomes, "Why are you shooting a 300 Win Mag, when Creedmoor ballistics kill the largest game, and very effectively?
Good question, the .300 mags are probably obsolete today given the bullets we have available. This wasn't always the case, I bought my 1st one in 1985 way before the Creedmoor. The one pictured is on it's 3rd stock, 2nd bottom metal, 3rd scope, and I'm quite sure the original barrel looks like a dry lake bed when viewed with a bore scope. I think I might keep it a while longer.
The .300 magnums are about as obsolete as my 2005 F150. It may have 170,000 miles on it but it has been well cared for and runs like a champ. The F150 was “retired” in 2012 when I bought a far more fuel efficient car for running around in and commuting to work. Both got me to work and back but there are a lot of thing the F150 can do that the smaller, more fuel efficient car cannot.
It is the same with smaller vs. larger cartridges. I regularly practice out to 600 yards and, while I can more easily hit the 4” steel at that range with my light kickers, such as my .243 Win, .257 Bob and 6.5CM, there is an important difference. For hunting purposes my .300WM delivers far more energy and velocity at that range.
Here are some examples, calculated for 600 yards, 7000 feet altitude and 50 degrees F.
2047fps, 1973fpe = .300WM, 212g ELD-X @ 2800fps MV (Hornady reload data)
2210fps, 1897fpe = .300WM, 175g LRX @ 3036fps MV (my hunting load)
1848fps, 1365fpe = .308 Win, 175g LRX @ 2600fps MV (Hornady reload data)
2138fps, 1421fpe = 6.5CM, 140g @ 2791fps MV (my hunting load)
The 175g LRX is what I use for elk and mulies in my .300WM. It delivers as much energy at 600 yards as my 6.5CM/140g ELD-M load does at 280 yards.
Same/Same? Not hardly.
