CO L UMN
•••
Frans Dreyer,
Manager
Senwes Grain
Brokerage is
the author of
this column.
tive-positive-negative. In this specific example there are three such
instances. The positive value of
absolute minima of the trend can
be traced back to a specific shot
number or load as indicated by
the green lines. The first instance
is (-52 / 22 / -24) with the positive
value 22 which agrees with shot 3
or 40.4gr. The second instance is
(-24 / 22 / -25) with the positive
value 22, which agrees with shot
5 or 40.8gr. The third instance is
(-16 / 4 / -20) with the positive
value 4 which agrees with shot 8
or 41.4gr. It is interesting to note
that each of the loads identified by
the Absolute Minima method is
also linked to a shot in the visual
ladder bundles as reflected in Figure 1.
Due to this confirmation I
decided to load shots 3, 5 and 8
as grouping tests. Four rounds of
shot 3 (40.4gr), shot 5 (40.8gr)
and shot 8 (41.4gr) were loaded
accordingly and shot at 200m. The
results of these grouping tests are
contained in Figure 2, Figure 3
and Figure 4 respectively and the
speed results of the shots in Table
2. In the end I decided on a load
of 40.8gr since the horizontal and
vertical distribution between the
shots were significantly smaller
than the other two and since the
standard deviation (Stdev) of the
speed between the rounds of the
same load was the lowest. To confirm I again tested 40.7gr, 40.8gr
and 40.9gr groups at a later stage
to ensure that 40.8gr was definitely the better load for this combination in my rifle.
HOW DO I USE THE LADDER AND ABSOLUTE MINIMA METHODS COMBINED?
The most important principle is
to “do the one and to not neglect
the other”. It is of the utmost
importance for a shooter to shoot
over a chronograph during load
development in order to jointly
and separately interpret the visual
ladder and Absolute Minima calculation. The node or stable point
determined by the Absolute Minima method indicates a load where
the variation in speed of the load
concerned will probably be stable
or will be minimised. The best
results are normally obtained when
Table 2: Speed and deviation from grouping tests.
No.
Grain
Ft/sec
No.
Grain
Ft/sec
No.
Grain
Ft/sec
1
40.4
2592
1
40.8
2620
1
41.4
2669
2
40.4
2570
2
40.8
2605
2
41.4
2649
3
40.4
2596
3
40.8
2607
3
41.4
2643
4
40.4
STDEV
2590
10.05
4
40.8
STDEV
2615
6.057
4
41.4
STDEV
2663
10.44
AVE
2587
AVE
2612
AVE
2656
the visual ladder forms a bundle
and the Absolute Minima method
identifies a load which forms part
of the bundle. Should more than
one corresponding load be identified, it would be advisable to test
both in order to identify the better
load, after which the loads of 0.1gr
on both sides of the most stable
load can also be tested.
GENERAL REMARKS
Always remember that safe and
responsible reloading practices
should enjoy preference. Be mindful of signs of pressure and stop
immediately should any signs of
pressure be experienced. Choose
accuracy above speed during load
development. Make sure of your
shooting technique and that the
gun rest is stable to ensure that the
gun is placed in the same position
every time before a shot is fired.
Each gun has its own recipe and it
is important to arrive at an optimal load for your gun by means of
a structured process. Apart from
all the possible "shortcuts" which
will help you to arrive at an accurate load, it is unavoidable for a reloader to go to the shooting range
on a regular basis. In the end it
is difficult to determine whether
a reloader shoots better groups
because the load for his gun is
optimal or because he spends more
time on the shooting range to
refine the art of accurate shooting.
I truly hope that the methods explained will make sense to you, as
co-reloader, to achieve the accuracy potential of your gun.
SENWES Scenario • AUG/SEP 2016
49