THE HANDLOADING BENCH 6mm NORMA BENCH REST (Part 6)
100 yards consistently running under three-inches at 600 yards despite the much greater opportunity for variable winds and other factors to increase groups in terms of MOA as distance and flight times increase. I initially eschewed VLDs, given their reputation for being ‘tricky’ but was eventually to end up loading the Berger 105gn VLD as my primary match round over 29.7gn of Hodgdon VarGet at around 2,730 fps MV.
Jewell 2oz BR trigger. Note the extension trigger blade shoe that had to be fabricated and fitted by Pete Walker to get it in the correct position below the stock.
2,900 fps is achievable at less than 60,000 psi pressure when you run combinations through the program but it consistently overestimated the velocities I got from my barrel by around 100 fps. If you’re in a similar situation to me and want a little more velocity, moly- coated bullets do provide it safely, using a modest increase in charge weights.
90 Grain and Up
As the rifle was originally intended for F Class, nearly all early load development used heavier bullets in the 90-107gn weight range. Back then, there was far less data around than now and we didn’t have Bryan Litz’s book Applied Ballistics For Long Range Shooting to give true G7 BCs and allow meaningful external ballistics comparisons. They show that for mid to long range work, the heavier – 105 to 108gn – bullets are always going to suffer the smallest wind drift and will give the best results - all other things (equivalent velocities and precision) being equal - as they’ll minimise the effects of any wrong wind call.
For shorter range shooting, the 90s and 95s will do fine and there will be no penalty in their use if you come up with loads that group well. One thing to note is that the 105s often seem to do better at longer ranges than their 100 yard performance might suggest – for example a load that produces 0.4-0.5-MOA at
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Talk of VLDs reminds me that I should mention bullet seating depths/jump to the lands. Tangent ogive bullets (Lapua Scenars, 107gn Sierra MK, Berger 108gn BT) were seated 15 thou’ ‘out’ and the two Berger VLDs 15 thou. ‘in’, the 105-grainer actually 17 thou’. There is no significance to that extra two thou’, they just happened to produce a round figure on the comparator-led value and the resulting setting happened to work well from the off.
6BR needs Small Rifle Magnum or BR primers.
I also tried the 105gn Lapua seated 10 thou’ into the lands and the 107gn Sierra seated 25 thou’ out (compared to my usual 15) as I’d read they sometimes appreciate such treatment – they didn’t particularly in my barrel. I’d used the 105gn Silver (factory moly- coated) Scenar as my match load in the early days through the H-S Precision stock period through to the restocking with the Shehane but once I discovered
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