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The following article appeared in Magnum of July 1999 and was translated from the original Afrikaans with the permission of the author and edited by him for accuracy.

7mm Lightning Bolt! - by Alf Smith


One of the outstanding factors of the development of hunting calibers in the 20th century, is probably the Magnum Movement that started gaining momentum with the introduction of the 375 H&H Magnum in 1912. Few realised that the H&H with the distinctive belt at the base of the case would take the world by storm and lead to a whole range of "magnum" calibers. It was particularly the Americans who were responsible for spreading the concept across the globe. Interestingly, there was a parallel development of calibers that could also qualify as magnums in Europe at the same time of the American belted magnums. These calibers never carried the magnum name and had no belt. Examples are the 8x68S, 6.5x68 and the 7mm's of Vom Hoffe.

Now all indications are there that the era of the belted magnum has come to an end. The last commercial cartridge that is likely to be derived from the .375 case has appeared as the 7mm Shooting Times Westerner (7mm STW). The new line of thinking is to use beltless cases such as the .404 Jeffery and .416 Rigby as basis for new calibres, witness Remington's .300 Ultra Magnum, the latest commercial offering.

Layne Simpson, the American gunwriter is the designer of the 7mm STW. He necked down the 8mm Remington Magnum case (which is based on the .375H&H) to .284 caliber to form the 7mm STW. Case length is 2.85" (72,39mm) compared to the 7mm Rem Mag's 2.50" (63.5mm) and the 7mm Weatherby's 2.54" (64,64mm). Case capacity at 93.3 grains of water is substantially more than the 83,2gr of the 7mm Rem Mag and 87,5gr of the 7mm Weatherby. This case capacity is the largest that the .375 case can be practically taken to. The larger case volume simply allows more speed - up to 300 feet per second more than the 7mm Rem Mag and 7mm Weatherby.

The 7mm STW with three of the smaller sevens, the 7mm Remington Magnum, 7x64 Brenneke and 7x57. This big 7mm delivers virtually the same punch at 400m as the 7x57 at the muzzle.

Because of a lack of availability of 7mm STW cases in South Africa, I fireformed .300H&H cases. The 300 case was necked down to 7mm and loaded with a 7mm Rem load. Cases formed in this manner are a little shorter than 7mm STW factory cases.



Increases in velocity result in flatter trajectories and thus increases the practical, useable range of a calibre. When viewed from the point of view of ballistic efficiency, calibres such as these are less efficient because they burn more powder per fps of velocity than for instance the 7mm Rem Mag. Simply put, you have to burn much more powder for small increases in speed. The downside is more recoil as well as higher temperatures which, in turn, reduce barrel life.

The 7mm STW was introduced in May 1988 and interest in the calibre was so high that it soon became one of the most sought after wildcats in the USA. The conversion from the 7mm Rem Mag is easy to do.

Utilising the full potential of any calibre in this class requires a special rifle and the first rifles in 7mm STW were built by the legendary Kenny Jarret of "Beanfield Rifle" fame. Beanfield rifles were originally built for use in soy bean fields where game needed to be taken over extended distances. These rifles deliver extraordinary accuracy and will do much better than an inch at 100 yards. Most will comfortably stay under a half minute of angle.

The secret of Jarret's rifles are in the choice of barrels (Schneider, Shilen or Douglas) and accurised actions such as the Model 700 Remington. Many accurising techniques such as pillar bedding are used in the building of these specialised machines. When the 7mm STW was introduced commercially, Remington took a lot of trouble over getting it right. The result was the model 700 Sendero in stainless steel and with a synthetic Kevlar stock.

The action beds down on an aluminium block around which the kevlar stock is moulded. The 26" barrel with it's distinctive flutes is free floated and the crown is recessed for protection against accidental damage. The shape of the stock, as well as the weight of 9 lbs, reduces recoil to comfortable levels. In theory, what should be quite a kicker, is actually no problem to shoot off a bench. When the Sendero became available in South Africa, I bought one immediately.

During December 1997 I did extensive testing with the majority of 7mm bullets that are available in SA.

Due to the lack of availability of reloading data with South African propellants, I used the 7mm Rem Mag as starting point in combination with data received from Advanced Gunsmithing Technologies of Potchefstroom. I used Federal 215 primers and S385, the slowest locally produced propellant. Somchem kindly made available a couple of tins of B12.7, a very slow burning ball powder developed for the .50 BMG. This propellant was too slow and even at suggested maximum loads I could not get consistent and accurate results. Speeds were also not what I had anticipated.

Cases for the 7mm STW were not readily available and I resorted to fireforming .300 H&H cases. Cases were necked down to 7 mm and I used 7mm Rem Mag loads to fireform. The formed cases had necks that were slightly shorter than the specification for the 7 mm STW.

The best groups were obtained with maximum loads and at overall cartridge lengths slightly longer than the CIP maximum of 3.650". The magazine box of the Sendero measures 3.70", which meant that most of my loads would not fit in the magazine and the rifle was used mostly as a single shot. The higher the speeds went, the smaller the standard deviation figures became. I kept a close watch on the primers, monitored the increase in speed per extra grain of powder and measured case head expansion to ensure that pressure levels remain acceptable.

I tested eleven different bullets in the 7mm STW: L to R: Hornady A-Max 162gr, Barnes X 175gr, Goodnel Plainsmaster 160gr, Goodnel HBPT 160gr, Nosler Partition 175gr, Hornady BTSP162gr, GS Custom HV 130gr, PMP 170gr, Nosler Partition 150gr, HornadyBTSP 139gr, Hornady Hp 100gr.

The twist of the Remington Sendero is 1 in 9.5" which should be ideal for 150gr to 160gr bullets. Several makes of jacketed lead bullets in weights ranging from 160 to 139 grains indeed gave excellent results. Gerard Schultz's GS Custom 130gr HV monometal hollow point was, however, the eventual winner. At a lightning fast 3750 fps (89gr/S385) with groups of 6 mm, I chose this load for my hunts in the Kalahari. This is a maximum load for this bullet and a compressed load. A hunting friend, Colin Angelo, also acquired a Sendero in 7mm STW and easily maintains 12 mm groups with the 130 grain GS Custom HV bullet loaded ahead of 85 grains of S385 for a speed of 3550 fps.

Prospective STW buyers must take note that some European manufacturers make bullets with a larger diameter than the American manufacturers. American bullets I measured were .2835" (7,2mm) while the European bullets varied from .2845" (7,23mm) to .2850" (7,24mm). These measurements may sound insignificant but in terms of pressure levels generated at close to maximum loads, the differences become very important indeed. I found it advisable to use reduced charges with European bullets. G S Custom offers two different diameter 7mm bullets in the HV range for American and European calibers.

With a 130gr GS Custom HV, the STW delivers the same energy at 400 meters as the 7x57 at the muzzle. Meat hunters will not like the STW, especially if forced to shoot at closer ranges. This lightning bolt caliber is intended for open country and for reaching where lesser calibers cannot. At close range the massive energy delivery of the STW is quite apparent and premium bullets are called for. The right choice of bullet for the STW is vital and bullet construction at these elevated speeds becomes a critical factor. Danie Liebenberg of Sauers gun shop in Kimberley fired several head shots, at close range, with jacketed lead bullets on an eland and all broke up prematurely. I took a head shot at close range on an impala with a 100 grain jacketed bullet. The bullet exploded like a grenade with massive damage the result.

Although this fast 7mm does well at the shooting range, it is when you take it out hunting that it really surprises. In August 1998 Colin and Gray Carterfield went hunting in the Boshoff district in the Free State and in the presence of the incredulous farm owner, shot a black wildebeest at a ranged 450 metres. The GS Custom HV bullet penetrated fully and was not recovered.

On the same hunt Gray took two shots at a springbuck and missed. The springbuck took off and after running a distance it stopped at 420 metres and looked back. And then Colin stepped in with the STW. The ram was facing them, presenting only a frontal shot. At the shot it fell instantly with a perfect neck shot!

My first opportunity for long range shots on game was in June 1998 in the Kalahari. I had already tested my loads on warthog in the Lowveld but the wide open spaces of the Kalahari would be the real long distance test for me. My first shot was on a springbuck ram at just over 400 metres. Unfortunately I pulled it low and as we found later, just nicked the skin on a foreleg. After the shot the group of rams remained where they were as they did not realise where the shot had come from. The ram that I nicked stood stamping his foot like an irate sheep ram. I aimed again and when the shot broke, he went down instantly. I was overjoyed, as it was a heavy animal with an exceptional set of horns. Meat damage was absolutely minimal.

Later on I also had an opportunity to take a red hartebeest. We were right at the top of a large dune. The herd of hartebeest was moving through the hollow below, towards the next dune at about 200 metres. When they paused for a moment, I dropped a big bull with a single shot to the shoulder. The STW was clearly living up to the promise of a great open country calibre.

The last shot of my Kalahari hunt was on a wounded animal. Bruce, my hunting companion, shot a red hartebeest standing on the summit of a dune. At the shot, the bull literally sat down on his back legs but was up in an instant and disappeared over the edge of the dune. We both took off running. I went for the spot where the bull had disappeared, while Bruce and the tracker went for a lower spot just to the right.

From the top of the dune I could not spot the bull and ran down the lee side at an angle. The next instant I saw him about 120 metres away. He was clearly wounded and I signalled to Bruce and the tracker that I had sighted him. Bruce signalled that I must shoot and, although badly out of breath, I managed to hold the crosshair on him long enough to squeeze off the shot. As the shot went off, it was as though an invisible hand pushed the bull over.

We examined the bull to determine what had happened to Bruce's shot, but could not find the entrance wound. Upon skinning the animal, we found what had happened. The bullet struck in the fold between the upper foreleg and the chest, but broke up completely before reaching a vital area. The GS Custom HV penetrated fully and performed flawlessly, as usual.

The STW has acquired a permanent place in my battery of hunting rifles. It must surely rate as one of the outstanding extended range calibres available today. It has power to spare for the largest of soft skinned game out to 300 metres and the flat trajectory is well appreciated by those who have difficulty with precise range estimation. May this big seven have a long and chequered career.

Colin shot this springbuck in the Boshoff district in the Free State. The distance was 420 metres.

 
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GS Custom Bullets,situated in Port Elizabeth on the East Coast of South Africa, manufactures solid copper, turned, monolithic bullets for hunting and sport shooting. These bullets are used by hunters on several continents, hunting from the smallest of antelope to the largest of dangerous game, using the smooth HP bullet, as well as the more popular HV, FN and SP bullets with the patented drive band concept. GSC bullets are configured for the highest possible ballistic coefficients. SP bullets are mainly used for sport shooting. All GS Custom Bullets are moly coated.