Englander -
The 9.3X62 is a real sleeper...sometimes compared to the 35 whelen, but this is a mistake. It has been so successful in Africa over many years that when the game laws restricted bores to a minimum of .40 caliber the 9.3X62 was almost universally exempted from the restriction.
The rim and case heads of the Mauser and Whelen have similar diameters, but the Mauser shoulder is 2.039 inches from the base, compared to 1.948 for the Whelen. In addition, the mauser tapers to .451 at the shoulder and the Whelen is .441. On top of this, most Mausers in this caliber have a 1 in 10 twist rate, which will stabilize very heavy bullets.
Held to COL 3.290 inches, it will develop over 4000 FPE, driving a 270 gr Speer to 2583 fps (H414 and Win 760). This is accomplished at fairly conservative pressures, since the round has been with us since 1905, and there are old rifles out there (Norma factory ammo is held to 50,000 PSI). In a long Mag action, you can seat your heavies out to 3.6 inches for a whopping increase in usable case capacity of 8 grains. This will take the Speer 270 grainer to 2675 fps, and that sounds a lot like a 375 H&H.
Nosler makes a nice 250 gr Ballistic tip in .366 with a BC of .494 with an SD of .267. They hold this to about 2600 fps, but that is conservative for work with a new rifle. This will track quite closely to factory 30-06 180 grain rounds in trajectory. Their 286 gr Partition has a BC of .482 and an SD of .307 if penetration is a concern.
The best news is that Hawk makes .366 in 8 increments from 200 grs to 320 grs. Jacket thickness runs from .030 to .050, and that is a LOT of options for a big bore rifle. For $2 a box, Andy at Hawk will cut crimping cannelures anywhere you want them, so things will stay put in the magazine when you touch off a 320 grainer...with an SD of .341 that one will drop a Rhino, and why not...its is really a 375 H&H in a small case.
Since African game is rare in England, a standard length action will work fine. I think the best deal out there in this caliber is the CZ LUX..I got mine in 6.5X55 and it is one beautiful rifle for $469, and the single set trigger is a dream. Controlled feed with the big claw extractor, and 5 in the box magazine. Unlike the "American" versions of the 550, it has enough drop at the heel that iron sights work very well, but it is still fine with low mounted optics.
If you are concerned about power, try to get one in a true Mag length action so you can seat to 3.6 COL. I would love to build one on a Sako 75 action...
