7mm Winchester Short Magnum

History

In 1963, Winchester introduced the .284, giving hunters optimum power in a short action rifle. The .284 never truly gained mainstream popularity due to the lever action rifle it was chambered in. The vast majority of hunters worldwide prefer bolt action rifles. In 2001 Winchester introduced the .300 WSM, a high powered cartridge designed for use in short, bolt action rifles. Following this Winchester released the .270WSM and 7mm WSM cartridges in 2002. 

Based on a grossly altered version of the 404 Jeffery’s case, the 7mm WSM has an overall length of 72.64mm and differs from its .270WSM sibling with a .96mm longer shoulder to prevent the possibility of a 7mm WSM cartridge being chambered in a .270WSM rifle. The overall lengths of Winchester's short magnums approximately .0590” (1.5mm) longer than those specified for the .308 family cartridges. The shoulder of the WSM case is 3.175mm longer than Remington's SAUM with a resulting 8% increase in powder capacity, this equates to roughly 50fps in barrels of equal length.

The 7mm WSM has become very popular worldwide as a hunting cartridge. Several rifle manufacturers support this chambering while ammunition is produced by Olin and Federal ensuring that it will remain popular in the near future.

The 7mm WSM was tested for a time among target shooters worldwide. Due to the shoulder safety design, the neck is very short. Many target shooters found this to be detrimental to extreme accuracy. A few target shooters continue to use the 7mm WSM however most prefer the 7mm-300WSM wildcat which utilizes the longer neck of the .300 WSM case design.
 

Performance

The 7mm WSM delivers best performance when loaded with 140 to 162 grain bullets. Unfortunately, longer bullets cramp powder space causing large reductions in potential velocity. Nevertheless, there are many excellent bullets for the hunter to choose from within these weight ranges.

Factory ammunition generates velocities roughly halfway between the .280 Remington and 7mm Remington Magnum. Hand loads tend to duplicate .280 Remington in order to extend case life.

The 7mm WSM is an effective and emphatic killer of medium game out to intermediate long ranges, producing best results inside 700 yards, much like the .280 Remington. 

One of the more desirable features of the WSM is that rifles can be fitted with a suppressor maintaining the same length and weight as a standard 26” barreled 7mm Remington Magnum.

   

Factory Ammunition

Current loads from Winchester Olin include the 140 grain Ballistic Silvertip at 3225fps, the 140 grain Accubond at 3225fps, the 150 grain PowerPoint at 3200, the 160 grain XP3 at 3050fps and the 160 grain Accubond at 3050fps. Actual velocities recorded is sporting rifles average about 30fps under these figures, an irrelevant difference.

The 140 grain Ballistic tip is best suited to lighter medium under 60kg (130lb) game at all ranges. It is a mild performer and is not designed to cope with close range shots on heavy bone. The 140 grain Accubond is a reliable performer on medium game up to body weights of around 80kg. Wounding at close to moderate ranges is violent, killing is very fast. Fastest killing is obtained at impact velocities above 2600fps or 290 yards. Beyond this range, wounding is thorough but less violent than at closer ranges. Delayed but clean killing normally occurs at around 2400fps and below (400 yards).

The 150 grain PowerPoint is a spectacular killer, again best suited as a lighter medium game bullet, producing explosive wounding but somewhat shallow penetration. At close range on heavy bone this bullet, like the Ballistic Tip, is prone to total disintegration.

The 160 grain Accubond is a very reliable bullet suitable for a wide range of body weights up to Elk sized game at 320kg (700lb). The Accubond produces fastest killing inside 225 yards; beyond this range, regardless of target resistance, kills can be slightly delayed but nevertheless clean. The 160 grain Accubond crosses the 2400fps mark at 350 yards, after which, wound channels decrease in diameter.

The 160 grain XP3 is a revised version of the 160 grain Failsafe. This bullet is too stout for fast killing on light or lean bodied deer and is best suited (as it was designed) to large, heavy bodied game. Readers are reminded that the 7mm bore does not produce wide wounding on large heavy game regardless of bullet design. The XP3 serves as a means to destroy the CNS of heavy game directly, requiring suitable shot placement.

Federal loads include the 140 grain Nosler Ballistic Tip at 3310fps, the new 140 grain Trophy Bonded Tip at 3200fps, the Vital-Shok 150 grain soft point at 3100fps, the 160 grain Barnes TSX at 2990fps and the new 160 grain Trophy Bonded Tip at 3000fps.

The 140 grain BT and 150 grain soft point Federal loads are similar to Olin loadings, suiting the same range of game. The 160 grain TSX is, as can be expected, best suited to tough game. The new 140 and 160 grain Trophy Bonded tipped bullets are untested at this time of writing.
 

Hand Loading

Olin factory ammunition is loaded to average pressures of 65,000psi in accordance with the WSM design parameters. It is impossible to supersede factory ammunition velocities without excessive pressure. Another factor that must be considered, is that although WSM brass is designed to maintain integrity at 65,000psi, case life is never as long as one would hope.

Realistic velocities when hand loading 24” barreled 7mmWSM rifles are 3200fps with 140 grain bullets, 3100fps with 150 grain bullets and 2920fps using 160 grain bullets. Some rifles may achieve velocities higher than those listed here. Best powders are slow burners in the N165, 2213sc (H4831sc) range. Hand loaders are advised to use standard large rifle primers (not magnum) in order to slow burning rates while at the same time maintaining optimum powder bulk density.

In custom rifles with longer barrels, ‘free’ velocity can be obtained along with a substantial reduction in recoil in comparison to factory rifles (depending on barrel contour). A short action 27” barreled 7mm WSM is approximately the same length as a 26” barreled 7mm Remington Magnum. Velocities for this barrel length are on average, 80fps faster than the standard 7mmWSM and the reduction in recoil can aid accuracy immensely.    

In single shot target rifle actions (no COAL restrictions) fitted with 32” barrels, the 180 grain VLD can be driven at 2950fps with low pressures. Full pressures are achieved at around 3050fps. Standard rifles with box magazines cannot fully utilize the 180 grain VLD due to decreased powder capacity resulting in low velocities. The 162 grain Hornady A-Max is the longest projectile that can be housed in a magazine fed 7mm WSM without loss of downrange  performance.

Due to the fact that the 7mm WSM duplicates the performance of the .280 Remington while being very similar to the 7mm Remington Magnum, the reader is directed to these texts for bullet performance.
 

Closing Comments

The 7mm WSM will likely remain popular for many years due to its ability to be housed in short, lightweight rifles. Unfortunately, the rifles are getting lighter because we are getting heavier and more unfit as a society. This is the key to the mainstream acceptance of the short magnums. These comments aside, the 7mm WSM is an ideal cartridge for experienced female hunters of a light muscular build who find rifles weighing over 8.5lb, to be burdensome. The WSM’s are also ideal for mountain hunters who work in extremely steep country, minimizing loss of balance/center of gravity during vertical rock face climbs.
 

Suggested loads: 7mm WSM					Barrel length: 24”
No	ID		Sectional Density	Ballistic Coefficient	Observed  MV Fps	ME Ft-lb’s
1	FL	Win 140gr AB	.248	.485	3195	3173
2	FL	Win 160gr AB	.283	.531	3020	3240
3	HL	154gr SST/IB	.273	.475	3050	3180
4	HL	162gr A-Max	.287	.625	2920	3067

 

Suggested sight settings and bullet paths
1	Yards	100	175	300	342	375	400	425	450
	Bt. path	+3	+3.9	0	-3	-6.1	-8.9	-12	-15.5
2	Yards	100	155	280	322	350	375	400	425
	Bt. path	+3	+3.7	0	-3	-5.7	-8.4	-11.5	-15
3	Yards	100	160	284	325	350	375	400	425
	Bt. path	+3	+3.8	0	-3	-5.3	-8	-11	-14.4
4	Yards	1`00	150	272	312	325	350	375	400
	Bt. path	+3	+3.6	0	-3	-4	-6.5	-9.4	-12.6

 
 

No	At yards	10mphXwind	Velocity	Ft-lb’s
1	300	5.3	2607	2113
2	300	5.2	2500	2220
3	300	5.2	2521	2173
4	300	4.6	2484	2219

 

Note: Load No 1 duplicates hand loads with 139gr SST/IB.

 

 

	Imperial	Metric
A	.535	13.58
B	.555	14.09
C	35deg
D	.537	13.63
E	.322	8.17
F	1.70	43.20
G	.243	6.17
H	2.100	53.34
Max Case	2.100	53.34
Trim length	2.090	53

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