6mm Variants

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Byron Pace gives a brief history of the two most common 6mm benchers calibres.

I had set out to explore the .220 Russian, given that it forms the parent case of many of the modern 6mm benchrest calibres. However, on putting pen to paper, I realised that for many dedicated hunters, this range of calibres falls outside those commonly found in factory rifles. Indeed, the closest most people will come to a 6mm BR, 6mm PPC or .220 Russian would be the well-loved .243 Winchester (hardly comparable to the ethos behind the world record-breaking 6mm). So I thought it may be beneficial to look at the history of the calibres falling in the 6mm benchrest class before following on in future articles to take a deeper look at possible hunting applications.

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Arrival of the Russian

The .220 Russian actually began its life as the 7.62×39 Soviet, a cartridge that has been the Russians’ official military medicine since the end of World War Two. This had limited use for the sporting rifleman, and found its niche mainly in the use of semi-automatic weapons (most notably the AK-47). In the late 1950s this case was necked down to form the .220 Russian, firing a 5.56mm bullet with similar ballistic properties to the .223 Remington, and found support among deer and varmint hunters alike. By 1965 it was produced by Sako, and this is where the story really starts.

Although there are few people today who still shoot the original .220 Russian, the super-accurate modern concoctions based on this case have found their way into the record books, as well as becoming a staple of modern benchrest shooting.

0101From AK to BR

The 6mm PPC was developed by Louis Palmisano and Ferris Pindel in 1975 – PPC standing for Pindel-Palmisano Cartridge – as a necked up version of the .22 PPC, which in turn found its parent case in the .220 Russian. The 6mm version dominates the 100-200 yard Group BR scene, and is regarded by many as the most accurate round ever invented over such distances. This is attributed to the small flash hole and primer pocket, combined with the short, fat shape of the case, conducive to efficient combustion and chamber behaviour.

The cases are easily formed directly from .220 Russian brass, which the vast majority of shooters source from Lapua. However, Sako standardised the calibre in 1985, allowing pre-formed 6mm PPC brass to be purchased. Today they have been joined by Norma, but the brass tends to be considerably softer than Lapua, and will not stand up to the repetitive reloading of ‘hot loads’. Most 6 PPC competition chambered rifles will not shoot the Sako versions, as they are marginally larger than the original. On request from the 6 PPC inventors, the standardised cases carry the USA tag after the calibre headstamp, in order to distinguish the two.

This calibre soon started to find its feet among varmint shooters, and a number of ‘off the shelf’ manufactures such as Sako, Kimber and Cooper Firearms began chambering rifles. The most commonly used bullet weights are in the 60-70 grain region, which offer 3,200fps MV and 1,481ft/lb ME with Sako factory loads. The trajectory is listed as +1.5in at 100 yards with a 200-yard zero, following on with a 7.2in drop at 300 yards.

From 6mm PPC to 6mm BR

If the 6 PPC is king of the short ranges, then the 6 BR takes over from 300-1,000 yards in terms of accuracy. Many of the characteristics that make the 6 PPC an inherently accurate and efficient calibre are also found in the 6 BR, although it takes its parent case from the 6mm Remington Benchrest cartridge. This gives it slightly greater case capacity, and hence the extra down-range ‘oomph’ and accuracy beyond 300 yards. Like the 6 PPC, the 6 BR is responsible for a hoard of world records, dominating 300-600 yard competitions. It is also known as the 6mm Norma BR.

This is in no way a complete overview, but it does give a bit of background for the two most common 6mm benchrest calibres. The 6 BR has fathered calibres such as the Dasher, 6 BRX and 6 BRDX. The .220 Russian also forms the parent case for the .220 Beggs and 6mm Beggs, both of which are outstanding rounds in their own right. We also have the lesser-known 6mm X (20-degree shoulder) and 6 XC (30-degree shoulder), but I will save this very interesting calibre for another month.  BP 

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