.270 Weatherby Magnum

History

The .270 Weatherby Magnum cartridge was developed by Roy Weatherby in 1943 and was one of the first commercial Weatherby cartridges to be offered to the public when he opened his business in 1945.
The .270 is one of a family of Weatherby Magnums which share a 2.545” (64.64mm) length case. These include the .257, .270 and 7mm Weatherby Magnum cartridges. The .300 Weatherby Magnum has a longer case length of 2.825" (71.76mm).

As with most of the Weatherby line of cartridges, the .270 gained a small but staunch following which has remained static to this day, regardless of new inventions such as the .270WSM. The .270 WBY is a favorite cartridge of Australian gun writer Nick Harvey for use on all game up to the size of Elk. Harvey has harvested a great number of game, including African plains game, using the 130 grain Barnes TSX.

Performance

As can be expected, the .270 WBY is a powerful, flat shooting, hard hitting cartridge. The Weatherby is not a specialized cartridge, regardless of its unique case design but rather, an excellent all-around medium game cartridge blessed with mild recoil (for a magnum).

Loaded with 130 to 150 grain bullets, the .270 WBY produces high shock for fast killing out to ranges of around 325 yards. Broad wounding continues out to around 450 yards after which, wound channels are more proportionate to caliber. Unfortunately, no manufacturer currently produces a wide wounding match style projectile in .277” caliber specifically for long range hunting at ranges beyond 500 yards.

The .270 Weatherby is absolutely ideal for light to medium weight game. On larger animals such as Elk, bullet choice has a huge effect on results. Using a bullet of sound construction, the Weatherby is able to render wide, fast bleeding wounds and free bleeding exit wounds on game weighing as much as 320kg (700lb). The .270 WBY is adequate for heavier species of game but certainly not as emphatic as something in the class of the .340 WBY.

Factory ammunition

Weatherby list one varmint load featuring the 100 grain Hornady soft point at a throat melting velocity of 3760fps. Other Weatherby factory loads include the 130 grain Hornady Interlock at 3375fps, the 130 grain Nosler Partition also at 3375fps, the 130 grain TSX at 3400fps, the 140 grain Nosler Ballistic Tip at 3300fps, the 140 grain Accubond at 3320fps, the 150 grain Hornady Interlock at 3245fps and finally, the 150 grain Partition, also at 3245fps. All of these loads are chronographed in 26” barrels are can usually be obtained in 26” length sporting barrels.

At close to 3400fps, the 130 grain Interlock is not a particularly good performer on medium game at close ranges due to bullet blow up. Nor does the Interlock produce a necessarily wide wound channel during bullet blow up due to its tendency to disintegrate into dust, rather than larger fragments. This load is best utilized on game weighing no more than 60kg (130lb). The 130 grain Partition is a slightly better all-rounder but is still put under a great deal of stress at close range, best suited to game no heavier than 80kg (180lb) for optimum performance.

The 130 grain TSX loaded to Weatherby velocities produces outstanding results. The combination of a high muzzle velocity plus a good BC, enables the TSX to produce high shock out to 400 yards (2600fps). There is a definite cut off point in performance when the TSX falls below 2600fps and rear lung shots often result in very slow kills, especially on light or lean animals. Nevertheless, this Weatherby load extends the ‘versatile’ or ‘shot placement forgiving’ range of the TSX out to a distance that is as far as many hunters are willing to shoot. This a good load for all game up to the size of, and especially suitable for, Elk.

Weatherby’s two 140 grain loads are also very useful. The Accubond and BT both have a similar form and will almost always shoot to the same POI. The 140 grain Accubond opens quickly on light game, causes immediate collapse with ordinary shoulder shots and renders a large wound channel. On heavy animals such as Boar or Elk, the Accubond will not exit from cross body shoulder shots, wounding is broad but the Accubond cannot be expected to produce optimum performance with heavily raking shots. The BT is almost always suffers bullet blow up at close ranges. This projectile is stouter than the 130 grain Hornady but at close ranges, is still best limited to use on lighter animals. As Ranges exceed 200 yards, the BT performs well on a variety of game up to 80kg (180lb) and continues to produce wide wounding out to around 500 yards.

The 150 grain Hornady Interlock really is a spectacular game bullet however it is not in anyway, a stout, deep penetrating projectile. Like the Ballistic Tip, this projectile is best suited to game weighing up to 80kg as a safe maximum. On heavy bone, the Interlock is prone to total disintegration. The Interlock is definitely a more spectacular, emphatic killer on light framed animals than the BT or similar conventional style projectiles.

Federal list three loads for the .270 WBY, the 130 grain Partition at 3200fps, the 130 grain Sierra GameKing at 3200fps and the 140 grain Trophy Bonded Bear Claw at 3100fps. These are fairly mild loads but are nevertheless useful. Both the Sierra and Nosler bullets will in most cases shoot to the same POI out to ranges exceeding 300 yards. The BC of both bullets is similar, regardless of the flat base of the Partition versus the boat tail GameKing design. Both Vertical and Horizontal dispersion between loads is either non existent or minute. The 130 grain Sierra is a hand grenade on light game at close to moderate ranges, disintegrating into fragments of copper and lead. The Partition is also a violent killer but does so without bullet blow up and produces noticeably deeper penetration. To this end, Federal sell the GameKing load at a cheaper price. Both the Partition and GameKing readily expand at low velocities of 2200fps.

The Trophy Bonded Bear Claw is similar to the Barnes TSX in design but different in performance. The TBBC has a wider meplat and soft lead frontal core. The BC of the TBBC is fairly low, a reflection of the singular goal towards optimum terminal performance within “traditional” moderate hunting ranges. The TBBC opens extremely quickly, renders a violent wound channel but also produces deep penetration. The higher the impact velocity or the heavier the bone, the more violent the wound. Like the TSX, this projectile does its best work at impact velocities above 2600fps which in this loading, equates to a range of 200 yards. Beyond this range, kills are clean but slightly delayed, becoming much slower at 280 yards or 2400fps.

Hand loading

There is little difference in powder capacity between the .270 WBY, the 7mm WBY and the 7mm Remington magnum. The latter has a slightly shallower shoulder angle and is shorter in the neck by a meager 60 thou (1.25mm). Nevertheless, Weatherby chambers feature generous freebore which allows for long peak chamber pressures, resulting in higher obtainable velocities.

From the factory ammunition COAL of 3.280” (83.3mm), bullet jump to the lands is approximately .375" (9.525mm). The hand loader can theoretically seat bullets closer to the lands but it is impossible to seat bullets within 40 thou (1mm) of the lands as most bullets will not be touching the case mouth, let alone seated deep enough for case to bore concentricity. The alternative is to seat projectiles at a midway point, focusing on concentricity and bullet grip above all else. The Weatherby Vanguard has a magazine length of 3.580” (91mm) while the Mark V rifle has a longer magazine again, adequate for long loads.

As far as potential accuracy goes, a small amount of freebore .150” to .200” (4-5mm) is usually quite forgiving while longer freebore is mostly detrimental to accuracy with short for caliber projectiles such as the 130 grain Sierra GameKing as well as low drag match style projectiles, the latter being mostly irrelevant to this cartridge. What tends to happen is that shorter projectiles will produce groups in the region of 1 to 1.5MOA with groups opening up in size as velocities are increased.

Using the 130 grain Sierra GameKing as an example, there is a moment when the projectile is neither gripped by the case or engaged in the rifling. During this moment, the projectile may in some instances become skewed in its flight, even if only by a fraction of a degree. The result is a loss in bullet stability which translates to yaw during flight. The twist rate of the barrel combined with velocity creates the final effect. The higher the velocity, the greater the yaw, the faster the twist rate, the greater the yaw. A point is reached where twist rate is no longer relative to the projectile manufacturers recommendations.
Fortunately, the .270 WBY has a 1:10 twist rate which is ideal for shooting long for caliber bullets at high velocities with good to excellent accuracy regardless of freebore. Properly tuned Weatherby rifles will normally shoot a variety of projectiles with acceptable accuracy, the point here is that the hand loader should have realistic expectations of this cartridge, there may be some bullets that will not work and in some instances, high velocities may not be obtainable with short projectiles due to poor accuracy. It is quite possible that some rifles can and do produce accuracy in the region of .5MOA however the .270 Weatherby was not designed for 600 to 1000 yard shooting.

The most suitable powders for the .270 WBY are the slow burners, especially H1000 (ADI2217), IMR7828 and N170. From 26” barrels, maximum safe working velocities include 3400fps with 130 grain bullets, 3300fps with 140 grain bullets and 3200fps with 150 grain bullets.

A few years ago there were very few projectiles capable of producing optimum performance in the .270 WBY, now there are several outstanding bullet designs. As with many high power cartridges of this type, a good rule of thumb for choosing bullets is to adopt either “light but stout” or “heavy but soft” projectiles. Of the two styles, generally speaking, the heavy but soft bullets tend to be the most versatile loads on medium game due to more uniform performance at longer ranges.

Examples of the light but stout bullets include the 130 grain InterBond, 130 grain Scirocco, the 130 grain Accubond and 130 grain Barnes TSX. Of the these, the core bonded bullets are a little more emphatic on lean game at longer ranges of between 300 and 400 yards while the TSX is much more thorough on larger animals.

The mid weight 140 grain Accubond is a good projectile, as already mentioned. A major strength of this projectile is that the shape of it’s ogive enables the Accubond to engage the rifling of long freebore rifles in as short a travel distance as possible, often resulting in outstanding accuracy. The Swift Scirocco is similar in design however Swift only produce a 130 grain Scirocco style projectile.

Examples of heavy but soft projectiles include the 150 grain Hornady SST and 150 grain Nosler Partition. Both are outstanding medium game projectiles. The Partition is more reliable on tough animals such as Boar while the SST, once annealed (see 7mm Rem Mag) is a versatile all-rounder, slightly better at longer ranges, producing very wide wounds out as far as 450 yards (2400fps). Neither are as effective as the Barnes TSX projectiles on Elk sized animals but for general medium game hunting, the excellent performance of the 150 grain Partition or SST cannot be under stated.

Closing comments

The .270 Weatherby continues to maintain a steady following, regardless of new inventions such as the WSM’s. The Weatherby is an emphatic killer of light to larger medium game and does so without producing horrendous recoil- two factors which will ensure it remains popular for many years to come.

Suggested loads: .270 Weatherby Magnum					Barrel length: 26”
No	ID		Sectional density	Ballistic coefficient	Observed MV Fps	ME Ft-lb’s
1	FL	WBY 130 TSXBT	.244	.466	3400	3336
2	FL	WBY 140gr Bal Tip	.261	.456	3300	3385
3	FL	WBY140gr Accubond	.261	.496	3320	3425
4	FL	WBY150gr Partition	.279	.465	3245	3507
5	HL	130gr Hornady InterBond	.244	.460	3400	3336
6	HL	150gr Berger VLD	.279	.532	3200	3410

Suggested sight settings and bullet paths
1	Yards	100	175	327	370	400	425	450	475
	Bt. path	+3	+4.2	0	-3	-5.7	-8.3	-11.2	-14.4
2	Yards	100	175	312	355	375	400	425	450
	Bt. path	+3	+4	0	-3	-4.8	-7.3	-10.2	-13.4
3	Yards	100	175	318	360	375	400	425	450
	Bt. path	+3	+4	0	-3	-4.2	-6.6	-9.3	-12.3
4	Yards	100	175	306	345	375	400	425	450
	Bt. path	+3	+4	0	-3	-5.4	-8	-11	-14.3
5	Yards	100	175	327	370	400	425	450	475
	Bt. path	+3	+4.2	0	-3	-5.7	-8.3	-11.2	-14.5
6	Yards	100	175	306	345	375	400	425	450
	Bt. path	+3	+4	0	-3	-5.4	-7.9	-10.8	-14.1

No	At yards	10mphXwind	Velocity	Ft-lb’s
1	450	11.4	2520	1834
2	450	12.2	2422	1823
3	450	11	2503	1947
4	450	12.2	2392	1906
5	450	11.6	2510	1819
6	625	21.6	2192	1601

Note: Load No.6 shows retained velocity at 625 yards as an insight to 2200fps velocity boundary.

270 weatherby magnum final.jpg

	Imperial	Metric
A	.531	13.50
B	.512	13.00
C	R.151
D	.492	12.50
E	.303	7.70
F	2.068	52.55
G	.397	10.08
H	2.549	64.74
Max Case	2.549	64.74
Trim length	2.539	64.49