I don't know the length of the Hawk 300 gr bullet so I couldn't run any numbers, but using a Barnes 300 XFB at 1.050" long, seated 0.250" deep, 2.90" COL I came up with this in a 20" bbl using a 325 WSM case...

71.1g Exterminator powder, 100% load density, 2412 fs/49525 CUP, 71.1gr H20 case capacity, 3875 FPE ME. Highest velocity with lowest pressure of all the listed powders.

Using a Swift 400 gr Semi P, 1.405" long, seated 0.405" deep, 3.10" COL, 20" bbl, 325 WSM case, this came up...

68.5g Varget, 100% load density, 2163 fs/55378 CUP, 65.8g H20 case capacity, 4155 FPE ME. Highest velocity at almost highest pressure and way the HE** too much for my taste...I think you would get a bolt welded to the case head not just stuck in the chamber a little bit.

I'm not sure how the higher numbers were derived but I think they are extremely optimistic or were developed with a longer barrel....or some kind of witches touch. Goin to a 24" barrel only came up with 2221 fs with the 400 gr bullet.

LD came up with higher loaded case capacities but no where near the 300 gr velocity even using 2230 powder.

The 416 WSM is an excellent cartridge but it still follows the laws of physics and ballistics.

I run my 416 Taylor about 2500 f/s with a 350 gr Speer and 2350 f/s with a 400 gr Hornady, both with RL-15, and you can get 2700 f/s with a 416 Rem and larger cartridges...but I would let you pull the trigger on some 300 gr load that calculates to 2700 f/s.

A 45-100, 2.6" length case would work in a SA and produces 458 Lott numbers with a 32" barrel, if you could get the feeding problem solved.

There are many cases that could be made to work fairly easily. I built a 458 WM on a SMLE action with a COL of 3.10". It must be loaded to the SMLE action's 45 KPSI pressure rating and at 9 lbs it is a "thumper" at both ends. Just about any SA could be converted by doing a little knowledge enhancing and for those that need a little more punishment and have deep pockets, a 50 cal using any number of different cases cut to the correct size.

The only reason for no factory SA's is NO one would buy them...there are already way to many already available and much more useful calibers and WAY to many recoil sensitive wussys.