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THE HANDLOADING BENCH


308 Winchester Rides Again By Laurie Holland


The ‘knockers’ are already out saying this pair will be too heavy for 308 Win - only any good in the 300 magnums. Certainly, we can expect people to reassess the old 30-338 long-range target shooting wildcat and its more modern short magnum competitors in this calibre for 1000 yard bench rest, maybe even give the ‘sevens’ a run for their money in F Class.


Using a 155 at 3050 fps as the baseline and working on equivalent MEs (3202 ft/lbs), you’d expect 2685 fps from the 200, 2560 fps from the lower BC 220, and 2450 fps from the only marginally higher BC 240. However, it’s unlikely that would work out in practice even in optimally throated chambers, as the SMKs have exceptionally long central bearing surface (or bullet shank) lengths.


While the Hybrid runs at 0.45 inches, the 220gn SMK measures 0.567 inches, and the 240-grainer an exceptional 0.69 inches - even longer than the bullet’s nose section length of 0.65 inches. Over-long bearing-surfaces increase pressures and reduce safely obtained MVs to a considerable extent. Also, back in the days when many US long-range any-calibre prone shooters used the 300 Winchester Magnum and similar cartridges with the 240gn SMK, it built up a reputation for shedding copper in the barrel thanks to friction and heat generated by the long shank.


Scaling


Berger’s Hybrids have been designed by the well known ballistician and Fullbore/Palma Rifle shooter, Bryan Litz


However, tell the Match Rifle competitors that heavier than 210gn bullets are unsuitable for the 308W and you might be surprised at the response, the old 220 and even 240gn Sierra MKs having been heavily used in this discipline in the past.


That’s the other ‘contra’ appearing of course – we’ve long had these heavy SMKs, so what’s new here? The MatchKings are antediluvian designs, the Hybrids are ballistics state of the art. That’s what! For instance, the new 200gn Berger Hybrid has a G7 BC of 0.320, while the SMKs get 0.310 and 0.332 for the 220 and 240gn models despite being 10 and 20% heavier respectively. The Berger can be driven faster due to its lower weight.


The other, more theoretical argument in favour of these bullets is that they are not exceptionally heavy for the


calibre anyway, only that our subjective expectations make them seem so. This is shown by looking at ‘scaling’ optimum weights by calibre. ‘Scaling’ is widely used by projectile designers – you have a near optimum weight and design in calibre ‘A’ that experience shows works exceptionally well and you scale its dimensions up or down as appropriate to get equivalent designs in calibres ‘B’ and ‘C’.


A good example of how this works is illustrated by development on high velocity 224 calibre rifles and cartridges for the military. Back in the 1950s long before the ArmaLite Corporation, AR15 and 5.56mm cartridge appeared, the US military undertook experiments in what was called the SCHV (Small Caliber High velocity) concept, codename Project Salvo. A US Army Proving Ground, Aberdeen, Maryland engineer took the pre-WW2 308 calibre


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