... Bell started out using the 6.5x55 and only switched to a 7x57 when he had a problem getting ammo.
Bell did not start out using 6.5mm.
Bell did not mention using 6.5x55, ..he did eventually employ 6.5x54 MS.
I don't know of Bell having supply problems with (.256 bore) rounds.
He also had issues with the long 160 gr. FMJ bullets bending and changing direction.
That is another interesting foot note and one I was not aware of.
I recall Bell remarking that ..256 did bend and .275 solids he wasn't too sure..... he still found them to hold
a relatively reliable (straight enough) course to the brain,....., .318 cal 250grain proved more reliable
in that respect. This was especially the case when performing oblique going away shots, where projectiles
had to navigate the neck before reaching the skull.
" I never saw a mangled or bent 7 mm. bullet, possibly because most of them had passed on whistling as they went.."- Bell, American Rifleman 1954.
".256 Mannlicher and :256 Mannlich· er-Schoenauer. Here we are approaching the limit of safety,
in diameter to length, for long traverses in heavy game. These long narrow four-diameter bullets bend
into the most extraordinary hook- like shapes and this oddity of theirs in- evitably brings under suspicion
their true course-holcling properties. I must say I only once failed to kill the animal fired at with the ,256
and that was due to a misfire because of a faulty round ...." - Bell, American Rifleman 1954
W.D.M. ‘Karamoja’ Bell, the famous elephant hunter who was a proponent of the 7x57 for the pachyderms,
stated the shorter bolt throw would have made the .308 Winchester the best elephant cartridge ever..
Isnt full bolt-cycle length of .308win and .30/06 the same in Pre64 M70s..?
Bell was merely speculating on the potential effectiveness of .308 win,
deep down his trust was with .318 because of real world experience with such....
"We now come to what I would take to Africa if I had to go through the whole thing again under the same set of conditions.
I would base my battery on a Winchester .308 Model 70 burning a cartridge loaded with a homogeneous bronze or Monel
metal bullet , of the form as worked out by Kohlbacker. At the same time, I would have a .318 barrel to fit the same stock and
a supply of 250-grain solid conventional lead- filled steel-jacketed bullets, just in case any unforeseen snags arose from the
use of homogeneous bullets in the .308." - Bell, American Rifleman 1954.
"Then coming down the scale we reach the .318 with its four-diameter 250-grain bullet. This is a killer. It holds its course
through almost anything and is superior in this respect to all other bullets I have tried. For oblique shots into large animals
it is quite the best...... I have a .318 weighing seven pounds ten ounces exactly, when empty. The deadliest weapon of
the push bolt type known to me." - Bell, American Rifleman 1954
[
"About ten per cent of bulls shot in the head received a second shot when using the .275, and this per-centage
was appreciably reduced when the .318 was used.- I put this down to the fact that the 250-grain bullet of the .318
held a truer course than the 170-grain bullet of the .275. - I know, too, that in the case of slanting shots from
behind where the bullet would have to traverse the im-mense neck muscles to reach the brain, the .318 long
250-grain bullet was more uniformly successful than the .275." -Karamojo Safari- (p.242-243)
"Broadly speaking, the best bullet for killing elephant is one which combines a good weight (it will not be easily deflected),
long parallel sides (this will help it keep course), good sectional density (not too much diameter to length), and a good but
not excessive velocity. - In my opinion the 250-grain .318, although far from perfect, approaches most nearly the big game
hunter's ideal bullet, followed by the 7.9 mm. or 8 mm. Mauser." - Karamojo Safari- (appendix p.291)