.240 Weatherby Magnum
Introduced in the Mark V rifle in 1968,
the .240 Weatherby Magnum was the last of a dozen cartridges introduced while
Roy Weatherby was alive. Physically, the .240 bears a strong resemblance
to the British designed .240 Apex or .240 Belted Nitro Express as it is more
commonly called. With a rim diameter the same as that of the
.30-06, the
Weatherby cartridge is suitable for any rifles with standard action
lengths.
The .240 Weatherby Magnum represents about all the powder capacity that can
be utilized with a 6mm bore with any degree of efficiency. When the 6mm Remington
and the .240 Weatherby are loaded to maximum chamber pressures in barrels
of equal length, the larger case will push all bullet weights 100 to 150
fps faster. Like other cartridges of low expansion ratio, the .240 needs
a long barrel in which to reach its impressive performance.
The .240 Magnum is an excellent compromise in performance. Its relatively
small bore size allows the use of lightweight bullets at extremely high velocity
on varmints without excessive recoil, yet with a trajectory that will give
any .224" centerfire a run for its money. Loading a 90 to 105 grain bullet
in the Big Six transforms it into a fine deer and pronghorn cartridge.
With the exception of light, varmint weight bullets, powders of slow burning
rate offer the best performance in this cartridge. Excellent choices are
H4831, H450, and
IMR-4831. With
the lighter bullets
H414, H4350,
IMR-4350,
IMR-4320, and
H380 are better
choices.
Source: Hodgdon Data Manual, 26th Edition
Historical Notes:
The 240 Weatherby was added to round out the Weatherby proprietary magnum
line in 1968. It differs from other 6mm's in having a belted case with somewhat
greater powder capacity. It is very similar to the 240 Belted Rimless Nitro
Express introduced by Holland & Holland around 1923. Thus far, it is
available only in the Weatherby Mark V bolt action rifle or through custom
gunsmiths. It is an excellent cartridge and will push the 100 grain 6mm bullet
with about 200 fps greater muzzle velocity than the
6mm Remington
and around 400 fps faster than the
243 Winchester.
However, a considerable portion of this ballistic advantage results from
increased barrel length and loading pressure. It is important to allow plenty
of barrel cooling time with this, and all, high intensity cartridges. It
is a more effective deer and antelope cartridge than the other two. The principal
detraction regarding the 240 Weatherby Magnum is that ammunition is expensive
and difficult to find outside of the large cities. The 240 case has about
the same capacity as the
30-06 and
the rim diameter is also the same.
General Comments:
The 240 Weatherby is the most powerful of the 6mm cartridges. It represents
the maximum performance that one can squeeze through a 6mm tube with modern
powders. The 244 H&H Belted Rimless Magnum, based on necking down the
375 H&H
Magnum case, will hold more powder but doesn't produce any improvement
in ballistics. The late Roy Weatherby built a successful proprietary gun
business on the basis of good product plus the all-important element of ballistic
one-upmanship. The weatherby magnum cartridges have traditionally offered
higher velocity and energy than their standard factory counterpart. The 240
was born of this same tradition. Of course Remington, Winchester, Norma,
et al have their own magnum line in various calibers, and Winchester offered
the 300 and
375 H&H
Magnums before WWII. However, Roy Weatherby was the first to really popularize
this British innovation in the U.S. He convinced the American shooters that
it was something they truely needed. For the hunter who must have that extra
edge in a 6mm rifle, the 240 Wetherby Magnum is the cartridge of choice.
Source: Cartridges of the World
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