Not the Alaskan. It is Mic McPhersons 510 Kodiak. 348 Win case expanded to take the .510 bullet.
I ran many bullets through the test rifle and the Marlin. Dug out the data today, it is a stack of paperwork about 2 inches high along with a 3 ring binder with the test fire date.
Highest energy load I found in the data was with the 450 grain Hawk. 5265 ft/lbs 2295 ft/sec. Eclipses the 458 Win a bit.
I used some 510 grain Woodleighs, the COL was too long to cycle through the action, had to single load. This is the bullet that exceeded 5500 ft/lbs. I do not remember if I kept the data due to the COL problems, but I am still looking, there are more files on this project tucked away in my archives. Just gotta find it!
Now it was 22 years ago when I was doing this. Combined with my 74 year old memory all the details are not at my instant recall.
I decided to revise this project as it bears mentioning to serious big bore guys. I will be running more test loads in the near future. Especially with the Woodleigh 500 grain bullet designed for the 50-110. This bullet has a very large meplat and carries a lot of weight forward, and the crimp groove is right where it needs to be for both maximum powder charge and cycling through the internally lengthened Marlin.
All the credit for this cartridge and rifle must go to Mic McPherson, he designed both the cartridge and the modifications to the Marlin. I am just a blue collar Machinist and carried out the work under his direction.
I lathe turned some bronze solids but never tested them. Next time!
And I have purchased NOE cast bullet molds for the rifle, I will be casting in a few weeks. Hard lead with gas checks.
There was a third party involved, he financed the project. Sadly I recently learned of his passing. This is what gave me the incentive to bring the project back to light.
Would I take on a Cape Buff with this rifle? You betcha.