Garandimal
member
.270 Winchester/150 gr.
The perfect hunting cartridge for North America.
If you take the American Legend 150 gr. M2 Ball .30-06 round, with its ~ 2,800 FPS Muzzle Velocity, and...
- Increase the Sectional Density of the Bullet to that of the mighty 180 gr. .30-06 round.
- Increase the Ballistic Coefficient of the Bullet to that of the mighty 180 gr. .30-06 round.
- Yet maintain the same Velocity, Rifle Weight, and Recoil as the .30-06/150 gr..
And accomplish this by:
- Reducing the Bullet Diameter from .308 to .277.
- Increasing the Chamber Pressure from 60,000 to 65,000 PSI.
- Maintaining essentially the same Belt-less Case and Dimensions.
...you have Excalibur - the .270 WCF/150 gr..
The .270 Winchester was initially designed as a 130 gr. High-Velocity, flat shooting cartridge in the mid-1920's(1925) - when Rifle Scopes were rare and expensive, and most rifles used "iron" buckhorn or Aperture sights.
Range-Finders, like Chronographs, were the realm of the Federal Government, so a high(er)-velocity round meant that one could hold on a target out to a longer distance before the bullet dropped away, known as Mean Point Blank Range(MPBR) - without using a "Kentucky Elevation" hold-over to compensate.
The down side is, the 130 gr. load tends to be destructive to edible meat at the normal, closer ranges that game is generally taken.
In an attempt to reduce meat destruction - heavier, 150 gr. Round Nosed bullets were tried, at a somewhat reduced velocity.
But, while less destructive, they are also less effective on game beyond "woods" ranges, due to the lower energy and increased drop.
Heavier, 150 gr. bullets, but of pointed "Spitzer" design, are a different story.
They have increased Ballistic Coefficients(BC), (the ability of a bullet to resist both Air Drag and Wind Drift), substantially greater than those of the 130 gr. bullets.
And the additional weight also increases the Sectional Density(SD) of the bullet, (its Mass/Area ratio), that generally determines how well any given bullet design will penetrate game.
So, generally, 150 gr. .277 Spitzer bullets have the same External(flight) and Terminal(strike) Ballistic characteristics as the tried and true (and heavier recoiling) 180 gr. .30-06.
And Slow Burn Rate Powders can push them along pretty well.
As more powder can be added, the heavy for caliber .277 bullets can be pushed at peak/high pressure for a longer period of time - resulting in increased velocity.
And while this produces "hyper" velocities in the 130 gr. cartridge that can cause meat destruction at "typical" hunting ranges (without careful attention to bullet selection) - the 150 gr. loads simply speed up to that of the 150 gr. .30-06!
The 150 gr. sptizer .270 WCF has the same Muzzle Energy and Terminal Energy down range as the 130 gr. loading... but does it with a Heavier, Higher SD(density) bullet that penetrates better, yet is generally not explosive to edible meat at closer ranges.
Excalibur!
Shoots like a 150 gr. .30-06... Hits and Penetrates like a 180 gr. .30-06.
...all in a < 8.5 lb./22" Bbl'ed scoped rifle, under the accepted 20 ft-lb of recoil threshold that is comfortable to shoot, (for all but the most sensitive shooters), ... all day long.
... meat in the freezer.
GR
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