The .375 Whelen Imp. is a really fun rifle, but I found it to be a handful for my one and only wildcat. I fireformed my cases using 13.5 gr of Red Dot and the rest of the case filled with corn meal topped with a glob of paraffin. Then I had to turn the outer case neck because the lower half of it was the thicker brass from the case shoulder. If I failed to turn it the finished cartridge wouldn't chamber. I learned all this stuff as I went along, and I had to disassemble a lot of loads to correct my mistakes.
The cartridge was recommended to me by an Alaskan friend who uses it in a Mauser and says it cleanly took anything. He said he liked it primarily for heavy brush because it dropped anything properly hit in it's tracks, minimizing the risk of losing the animal if it ran.
All things considered, I wouldn't recommend wildcatting because it's a lot of trouble for a questionable benefit. I did it because I'm a tinkerer. I'll say that I learned a lot from the experience though. A 45-70 or a 444 Marlin would probably accomplish the same thing. If one was determined to load a wildcat I'd recommend something less radical than the .375 Whelen Imp.
I found out not long after I had committed to the wildcat that there is a very popular European round called the 9.3 x 62 which is very similar in performance, and is available commercially (providing you want to open the vein to NORMA), and Barnes and Nosler publish data for it.
I never hunted with the rifle and it languished in my safe for a few years, until I recently learned bullet casting and that's when I came to really love that rifle. I installed a Kiplinger single-set trigger, and sent the scout scope to Leupold to change the reticle from heavy to fine. I now load a Lyman 270 gr. flat-nose gas check bullet over 38 gr. IMR3031, giving 1950 fps at the muzzle. It's very accurate with that load, and I consider it one of the most enjoyable target rifles I've ever handled. It's cool looking and it usually get some attention at the local range.
I don't have any experience with the 6 Remington, though I found a box of it in my garage a few years ago and I have now idea how I got it. I definately share your opinion of the .280 Rem. I owned a Ruger 77 chambered for it and put two whitetails and an elk in the freezer with it. I particularly liked it with Hornadys 162 gr. Spire Pt. I gave it to my brother in law some years ago and I miss it. My only 7 bore now is a Ruger No. 1 International in 7 X 57 Mauser. One other thing about the .280. I had a friend who shot Distinguished Grand Master (sounds like the Ku Klux Klan huh) in DCM High Power matches back in the late 80's using a bolt rifle chambered for .280. He used Sierra 150 gr. Match Kings.
Shoot safe brother.
A super fine rifle that is no longer made. I have yet to see one in any caliber that wouldn’t shoot less than 1” groups at 100 yds.
They were only produced for a few years and were too expensively built to sell with the Marlin name.
243 25/06 270 280 rem and 30/06 are the only calibers that I know they were produced in.
If you ever find one used ( hard to find because nobody will sell them if they have shot it) buy it!
They are equal or better in every feature to any of the better bolt actions out there.