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cups in the cartridge and CCI’s 450 (SR Magnum) or BR4 versions are the favoured varieties proving to produce excellent results while being amongst the toughest of the bunch.


The Russian manufactured PMC/Wolf SRM is another good choice in my experience. Remington 7½BR and Federal 205M models perform well in the cartridge but have ‘softer’ cups so cannot be used with quite as hot loads as the CCI products. Never, ever use ‘standard’ SR primers such as the CCI-400, Federal 205, PMC/Wolf SR and Remington 6½ which have thinner cups (0.020” v 0.025” in magnum/BR versions) and were designed for lower pressure cartridges such as the .22 Hornet, .218 Bee and .222 Rem.


the cartridge’s design, in particular its case being dimensioned for the small primer and given an undersized flash-hole diameter. The 6BR case is one of only a very small number of designs that use small primers in what I’ll unscientifically call full-diameter cases.


The others are the .220 Russian/PPC family, 6.5X47 Lapua and that company’s .308 Winchester ‘Palma’ brass. Outside of the precision shooting field, you’ll find small primers used in old UMC headstamped 7.62X39mm brass (Remington manufactured); current Hornady plus Silver State Armory versions of the 6.8mm Remington SPC, but these cartridges all use the standard (larger) diameter flash-hole.


There are two issues here – primer and flash-hole size. Taking them in that order, why use a small primer? The reduced amounts of heat energy and weight of hot particles injected into the powder charge column are better matched to the 28-40gn charge weight range seen in the PPC to 6.5X47L cartridges giving more consistent ignition and making it easier to achieve small MV spreads and groups. As an aside, the small primer/flash-hole combination is only marginally effective when you get up to the 308 Win sized case and 45-50gn charge-weights as many users of the original Remington UBBR cases found when they used them in as manufactured 308W form, especially in cold weather. Several North American ‘old hands’ have expressed their doubts about the wisdom of resurrecting this combination in Lapua’s 308W ‘Palma’ cases, a subject I’m currently investigating through side by side tests of various powder/bullet combinations in standard and ‘Palma’ brass.


Anyway, use of the Small Rifle dimensioned primer is uncontroversial in the BR but is not entirely without downsides, this being in the form of a much greater propensity for the firing pin tip to crater and in extremis pierce this size of cap. It is helpful to use ‘magnum’ or BR primers with their thicker brass


The other and equally important side of this particular equation is the firing-pin fit in the bolt face. Any custom target action should be trouble free but factory rifle bolts are often a different matter. Recent small-diameter firing-pin Savage actions are the best of the bunch but even they will produce problems with heavier, higher pressure loads that a BAT, Barnard, or RPA will take in its stride.


Remington bolts/pins are variable in this respect – my 700 based 6BR Light Gun copes with ‘reasonable’ loads and velocities. Conversely, the Winchester 70 action in an originally .308W calibre FN SPRA4 (Special Police Rifle) that I had rebarrelled to 6.5X47 Lapua has proven almost unusable with severe primer extrusion and ‘blanking’ with loads barely above Vihtavuori’s starting levels. (By the time you read this, it should have been rechambered to the LR primer using 260 Rem which will solve this particular problem.)


Greg Tannel (Gre’-Tan Rifles of Colorado, USA) offers a cure in the form of a very reasonably priced firing-pin turning and bolt body bushing service with a one-week turnaround to American FN/Winchester, Remington and Savage shooters in this pickle but we don’t have anybody offering such a service in the UK to my knowledge.


1.5mm Diameter Moving onto the flash-hole, our four SR primer / small flash-hole designs are specified for a nominal 1.5mm (0.059 inches) dia. aperture (compared to 2mm / 0.080 inches for everything else) and an immediate problem here is that the standard decapping pin diameter used in sizer or dedicated decap dies is 0.0625 inches, so use of same in the BR case will likely see the pin stuck in the flash-hole, broken, or if rigid enough surviving at the expense of crudely swaging the flash-hole out. Shooters have drilled the flash-holes to the ‘normal’ size or somewhere close to overcome this ‘problem’ but tests invariably show this increases group sizes and MV spreads.


You should get a suitably dimensioned pin with your Target Shooter


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