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- Last updated: 14/07/2017
Often obscure cartridges are wildcatted or more popular cases resized and necked up/down to achieve benefits either noticeable or less so. One area popular in Britain is long range shooting. F Class sees some serious kit and odd calibres compete these days and every bit of advantage a new cartridge can give you in competition is taken seriously.
Me, I love my long range varminting, be that at hooded crows or rabbits or just plinking away at steel silhouettes at extreme range. One calibre that still proves popular is the 6mm/.243”. Case capacity is usually small/medium yet offering highly efficient combustion. The other is that heavier weight 6mm bullets are ballistically efficient, like their bigger brother the 6.5mm, the 105-115 grain 6mms offer a lot down range. They also kick less so spotting shots is easier and barrels last longer, win win.
Simplicity is often best in ballistics and a slight tweak here, a small modification there and you have yourself a classic case. The 6.5mm x 47 Lapua has taken the shooting world by storm since its introduction in 2006 and it has been modified ever since. My contribution was the .20 and .22 Satan, based originally on the 6mm x 47 Swiss Match case and then the newer 6.5 x 47 Lapua.
It wasn`t long before the case was necked down to 6mm and voila - a superb, long range, mild mannered cartridge capable of shooting heavy bullets at 2800 -3100 fps with ballistic coefficients (BC) between G1 Value of 0.400 to 0.550.
Outwardly this range of cases are based around the .308 family with a 0.473” rim diameter but overall length of 1.850” for a max cartridge length of 2.600”, to allow it to be used in shorter bench rest style precision actions.
More importantly the parent case has a small primer pocket, which is supposed to yield more consistent ignition, although I have to be honest in both the .20 and .22 Satan rounds using Swiss Match and Lapua brass I found little difference, but then I am not a bench rest shooter!
Capacity-wise, at 47-grains of H20, it’s larger than the excellent 6mm BR, which has a 38-grain capacity, is similar to the vaunted 6XC with 49-grains; however the 6mm x 47 Lapua uses superb brass and is bigger than the 6mm Dasher with 41-grains. It is almost the best powder capacity for that 3000 fps sweet spot on velocity that 6mm bullets sing at! My 6mm PPC achieves this with a 65 grain pill, whereas the 6mm x 47L does this with a 105-grainer for only 8-10 grains extra powder.
The case is formed by simply necking it down from 0.264 to 0.243” from the parent case with no other modifications. The shoulder angle is 30° but the side walls are pretty parallel at only 0.471 to 0.455” reduction from case head to shoulder. You can improve this if you like with a 40° degree shoulder like an Ackley, but it’s for looks only really and pushing the shoulder forward to increase powder capacity will reduce the neck length which on the 6mm x 47L has the benefit of supporting the longer bullets, so best left alone.
If you were going to build it as a walking varmint/small deer and fox rifle, then a 1 in 10” twist rate would be fine for lighter bullets up to 80-grains. A friend had a re-barrelled Rem 700 with a 1 in 12” barrel, actually a .243AK (28”) with the chamber cut off and then rechambered. It shot a treat and was a good way to re-cycle a fire cracked throated old barrel to its new 24” length. That slower twist rate rifling was easy on bullets at that speed, so as not to tear them apart with rotation torque, without the high-pressure issues.
The real purpose of the 6mm x 47L however, is to handle the heavier bullets. Here a Krieger, cut rifled, 1 in 8”, stainless steel, match grade, heavy profile tube was fitted as a switch barrel for an RPA Quadlite action. 28” as a sitting or prone varmint rig really brings the best from the calibre. When stoked up a bit most of the loads are 100% load density with medium to slower burn rate powder you need those extra inches to get a 100 fps or so velocity benefit. Fitted with a sound moderator, recoil is reduced still further as well as noise, every shot can be seen, so instant trajectory or windage correction is possible as you shoot!
You can, if you want, go the neck turned route and have a light clean up with a 0.270” or thinner 0.264” neck diameter with loaded bullet, so as to benefit from the consistent neck tension and fitment within the chamber. This Krieger was chambered by Steve Bowers, who used a standard reamer from Pacific Tool and Gauge, and achieved a 0.273” neck diameter on the loaded bullet.
The other thing to sort out is throat length as the 6mmx47L is throated for the heavier longer bullets to maximise the case’s powder capacity, so using shorter lighter bullets may have to be seated much farther away from the rifling lands. I have shot a few custom 6mm Lapua`s now, here`s the data from the RPA
Again Quickload and Quicktarget were excellent for predicting loads and down range trajectories, and the new Berger reloading book now has data for the 6mm x 47 Lapua, albeit in a 24” barrel. You instantly notice the mild report, which is helpful if out long-range varminting or steel silhouette shooting, where numerous shots are the norm. This allows you to really concentrate on trigger pull and follow through for extreme accuracy. This is also helped by almost negligible recoil for this heavy 14.5 lb, all-up rig.
Best load was the Berger 115-grain, Match VLD bullet with a corking BC of 0.545 and when loaded with 40-grains of Alliant RL19, slightly compressed, that 28 inch tube gives 2972 fps. At 100 yards, all five Berger’s cut just one big hole! At 300 you could hit a golf ball nearly every time and at 500 it was averaging 2.5-3” when the wind was playing ball.
Zeroed at 200 yards you are -6” low at 300, -18” at 400 and -36.5” at 500 yds. Wind-wise those high BC`S are really slippery, with a 10mph wind at 3 o’clock you are only 4.8” off at 300 yards and 14.6” at 500, so very easy to adjust for. Extend the range a bit to 750 yards and it is -116.5” low and out there at 1000 yards you are -263.05”with 34 and 66” wind drift respectively. Compared to a .308 Win 150-grain SST doing 2800 fps you are -46.5” low at 500 yards with 21.45” wind drift . At 1000 yards you drop -378.5” with 107”drift, so quite a difference in favour of the 6mm x 47L.
If you want a nice deer bullet then the 90-grain Nosler Ballistic Tip with 39.5-grains of Hybrid H100V powder gave 3122 fps for 1948 ft/lbs and key holed all groups!
Another interesting cartridge that has found favour with mid to long range shooters in this country. Due to its minimal 6mm calibre, it is ideally suited to both target and deer/vermin use with the correct bullets.
Its mild manner and frugal powder consumption makes it very efficient, with its low recoil making it very user-friendly. Plenty of reloading kit, bullets and powders are available for this 6mm and if you fancy a different cartridge than the 243 AK for long range, then the 6mm x 47L has a lot going for it.
Steve Bowers Custom work 01242 863005
Norman Clark reloading kit 01788 579651
Reloading Solutions reload kit 01865 378200
Edgar Brothers Hornady, 01625 613177
Alliant and Hodgdon powder RPA, Range master Precision 0845 8803222
Henry Krank Sierra bullets 0113 2569163
JMS Arms Quickload and MAE Mods 07771 962121 www.quickload.co.uk