or read on, looks interesting.
The Incremental Load Development Method
There is a load development process I used more than l0 Years that can tell you quite
a lot about a rifle and that kinds of components it likes and at what velocity levels it will
shoot best. I first read about this method in an article by the late Creighton Audette
entitled, "It Ain't Necessarily So". This article appeared in the NRA's National
Championship Training Clinics Manual Series in the volume, High-Power Rifle
Shooting, Volume III. I never saw this load development method mentioned anywhere
else, although Creighton may have published something on it in Precision Shooting
back before I became familiar with the Magazine.
I once commented that some of these NRA manuals had been out of print, for indeed
some of them had been. The NRA has informed the Precision Shooting editor that all
three of the High-Power manuals are now back in print. These manuals contain a
wealth of Information for High-Power shooters, not found anywhere else.
I tried Creighton's method. It is simplicity itself and certainly seemed to work well
enough to tell me which loads would give me the best accuracy in my rifles at
reasonable velocities and pressures with a particular bullet.
Creighton Audette's Incremental Load Development Method (or ILDM for short)
essentially is: Choose a bullet, primer, powder and case brand. Once you have
chosen these things, there are two numbers you need to choose to use this method: A
starting load and a load increment. With that chosen, load 20 rounds, start with the
starting load and increase the charge weight stepwise by the increment you chose for
each subsequent round. Load only one round with each charge weight. Then, using
the same aim point, fire all these rounds on one target and interpret the results. Here
are the details.
For medium case capacity cartridges such as the .308 Win. or .30-06 Sprg. Audette's
standard increment was 0.3 grains. For small cases such as the .222 Rem, .223 Rem
and the like, use 0.2 grains. For medium-large Cases such as the .30-338, 0.3 shall
also do. For really large cases, so large that I don't know of anybody who is crazy
enough to bench test them a lot, pick anything you like, 0.5 or even 1.0. It's your
Your start load (charge weight) should be simply the maximum charge weight for that
cartridge with that bullet minus a decrement, that is 20 times the increment. Example: If
you choose an increment of 0.3grs., the decrement would be 6.0 (= 20 times 0.3). In
this example the decrement would be 6 grains. Make sure your starting load is a safe
load. If you use a really slow powder, such as 4350 or slower, do not go below the
recommended minimum load for that powder to avoid the risk of secondary explosion.
The secondary explosion effect occasionally occurs with light loads of slow powders,
or partly empty cases. It does not happen every time, but is frequent enough and
dangerous enough, that almost all load manuals now list minimum charge weights. For
you safety, never charge a case with less than the minimum recommended charge for
Incremental Load Development Method
a specific powder.
Next, load up a set of test rounds by loading only one round, that's right, only one
round, with each charge weight. Start with the starting load and load one round. Then
load the next round with 'starting load + Increment'. The next round would be starting
load + increment + increment. The next, starting load + increment + increment +
increment. You step up a Ladder. An example will make this clearer.
Example: If the starting load were 40.0 grains of 4895 and your increment is 0.3 grain,
You would load the 1
st Round with 40.0 grs., the 2nd with 40.3, the 3rd with 40.6, the
4th 40.9, the 5th 41.2, the 6th 41.5, and so on ... . Twenty incremental loads will take
you the Ladder up from 40.0 to 45.7 grains in 0.3 grain steps. When loading it is
important to keep track of which charge is in each case. An easy way to keep things
orderly is with a fine tip marker, like a Sharpie, write the charge weight on each case
just before charging the case. Approximate weights are not good enough; weigh each
charge to a tenth Grain (1/10 gr.).
Once you have 20 rounds loaded, store them in a shell box starting with the lowest
charge weight incrementing to the highest charge weight. This way you know precisely
what charge is in each particular shell. Marked cases are a good safe guard against
confusion. Now starting with the lightest charge, shoot them in charge weight order. To
learn the most information from your efforts, there are some precepts you should do
prior to beginning the test. They are:
Start with a clean barrel and shoot about 5 fouling rounds, loaded with the
starting load before you begin the ladder test. Shooting the fouling shots achieve
several benefits: (1.) Fowlers allows you to get on target and gives you a chance
to move your group on the target to a desired aim point. (2.) Fowlers give you a
chance to properly adjust the position of your Chronograph screens. (3.) Fowlers
fowl the barrel properly with powder foul from the powder used for the
incremental Ladder test. This last item is important: After firing with one powder
and then changing to another powder, even though both powders were from the
same manufacturer, all too often a barrel needs as many as 4 or 5 rounds to
"settle down". I don't know whether changing primers, while using the same
powder would have the same effect, but it might. To begin with a clean bore and
then to foul it with group shots with the starting load results in a controlled test
Starting with lightest charge round , shoot the ladder test rounds in increasing
charge weight order. When you are approaching the maximum load level watch
for signs of excessive pressure. If they appear, stop!
If possible chronograph all shots. Velocities should monotonically increase, but
an occasional Oddball shot may yield an off-order-velocity. Logging velocities
helps you to interpret the target. The chronograph has occasionally helped me to
determine the powder charge, when I shot a round out of order.
This step is the key to the method: Shoot all rounds on the same target using the
same aim point. Number the shots and shot holes to identify which shot caused
Incremental Load Development Method
which hole in the target. Make good notes. Always be sure to write down any
pertinent data, such as the fact that you saw the crosshairs fade to the right, or
down, or wherever for any particular shot. This information is needed to interpret
Shoot the test at a goodly distance, at least 200 yards, but 300 yards is better.
Creighton advised in his article to use 300 Yards. The problem at 300 Yards is
that it is very difficult to identify the shots by number on a target that is that far
away, unless you have a superior spotting scope, and it is a very calm day with
no mirage, or use an electronic target system. The Ladder test can work at only
100 yards, but sometimes it is hard to discern what happens on the target. The
first time I ever tried this method was at 100 yards with a new Obermeyer barrel
that set 14 shots into a 1.25 Inch hole. That was kind of hard to interpret.
A 300 Yard range with target pits and pit pulley is the best scenario. Pull the target after
each shot and number each shot hole with a pencil on the target face, or put numbered
white Pastem's over holes that are in the black. At 200 yards, the shot holes can
usually be seen, but when a tight cluster occurs it is hard to identify which shot is
At any distance on a pit-less range, you will have to resort to plot the shots by number
on a target diagram. While you shoot have someone else watch the target through a
spotting scope. Another good idea is to use Birchwood-Casey Shoot-N-C targets.
An important guide to successfully learn from a ladder test, is to set up the rifle exactly
the same way as you intend to use it later on. This means, if you intend to use the rifle
with a scope sight, then shoot the test with a scope on the rifle. If you intend to shoot
from a rest, or other support, use the same rest, the same way.
If you are going to peep the target through iron sights (as in High-Power competition),
then shoot the test with the iron sights you intend to use on the rifle.
If you shoot a ladder test with a rifle configuration set differently than the intended use,
the rifle's recoil and vibration characteristics will differ enough that the load may not be
optimum. Shoot any ladder test with the rifle set up the way you are going to use it!
After you finished shooting the rounds, you will have two data collections, that when
looked at together can tell you a lot about your rifle. They are: the data sheet listing the
loads and their velocities and the target with the numbered shot holes, or the target
together with a target diagram with shots numbered. The target with the numbered shot
holes is the most important.
To plot shots on a target diagram and to have the target itself to compare to the
diagram is very useful. Usually this helps to correct the diagram and enables to
number most holes in the target.
Interpreting the Data
Incremental Load Development Method
I can hear the wheels turning in your minds out there. You all ask, "How in Hamburger
Helper can this mess tell me anything. The answer is simple, but you need to know
what to look for. While ignoring the chronograph results look first at the target. Are there
any places on the target that produced a halfway decent group?
As velocity increases the shot holes will usually pattern upwards on the paper. The
lowest velocity shot will usually hit the target lowest. The highest velocity shot will
usually hit the paper highest. In this upward ladder there will usually be clumps or
groups of shots. These are the most important of all. Sometimes the groups will be
round, other times the groups will be vertical. If the test was preformed in a windless
environment and the holes scatter from left to right as well as up and down, it is
probably time to try another powder or primer and/or check the bedding of the action in
However, with any powder and primer combination the following usually happens.
Within the 20 bullet impact pattern on a target, five or six consecutive shot groups can
be found. This is not random. The numbered shot holes will march up the paper then
stop for a few shots in a group before jumping out of the group and then resuming their
The key to interpreting the pattern are all numbered shot holes. You could shoot with
all sorts mixed loads with different bullet weights, different powders and primers,
different cartridge cases brands, etc., 20 shots at one target and probably get a few
nice three or four shot groups and maybe even a small five or more shots group
somewhere in the 20 hole pattern in the target, but that wouldn't mean anything. Even
with all matched components and everything else done correctly with the ladder test, a
small group would not mean anything, unless that group was made by consecutive
shots in increasing weight charge order.
We only look for small groups formed by consecutive shots. We call such groups
"Sweet Spots". In a Sweet Spot, the fired Rifle "cares not " about the powder charge
weight, as long as it remains in a certain range. The ladder test purpose is simply to
pick a charge in the middle of the Sweet Spot group charge weight range. One benefit
to find a load with this method is, a load, tolerant to minor powder charge weight
variations. Even if your powder measure technique is not accurate, the Incremental
Load Development Method (ILDM) with the ladder test will show a load to be accurate
with thrown charges.
The Ladder Test works because ...
If you look at the reason the right way, it is simple. As the powder charge increases, thewith barrel vibration and barrel time effects.
muzzle velocity also increases, but the time the bullet accelerates in the barrel (called
barrel time) decreases. As powder charge and muzzle velocity increases, recoil also
increases, whipping the barrel. I believe the recoil induced muzzle elevation interacts