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Hand loading and the Ladder test.
When hand loading ammunition. Getting the most powerful, accurate and safe hand loaded ammo can be a time consuming, expensive and frustration experience. When searching for an accurate load, the ladder test might help you speed up the search process and save you some cash at the same time.
Below is a “How to” guide on ladder testing hand loaded ammunition and is the process that I have used over the last few days to find an accurate load for my .338 RUM.
A good starting point with a new rifle is to sight in the rifle using factory ammunition. This not only gets your scope lined up with the target, but it also gives you some empty cases to use as a reference to help you determine the safe maximum pressure to load your ammo too when determining powder charges.
The next step is to load up some ammo using the recommended powder charges in a quality reloading manual. When using ADI powders, I use the loads recommended in the current ADI hand loaders guide.
Start off with the minimum load of a suitable powder, listed in the hand loading guide for your cartridge and projectile combination. Load up one cartridge with this load then load up another with a slightly heavier charge. Keep loading up cartridges in small even increments until you are near the maximum listed in the guide.
These increments can be 1 grain for large magnum cartridges or 0.3 grains for the smaller varmint size cartridges. Never exceed the maximum powder charge as listed in the hand loading guide and approach the maximum charge with caution.
Once you have loaded up a few cartridges it is time to test them at the range. For a ladder test I prefer to shoot at longer distances past 100 yards. For low velocity cartridges 200 yards is fine but for high velocity rounds, I would shoot at a minimum distance of 300 yards.
Start with the minimum charge weight and fire at the target. Identify where the bullet landed. Let the barrel cool for 5 minutes then fire the second lowest charge. Repeat this process until you have fired all your cartridges at the target. Always check for pressure signs after firing each cartridge. Approach the maximum charge with caution. If you get high pressure signs with a particular load then stop shooting. If you have a chronograph, measure each shot and record the velocity given.
Pressure signs……New, unfired cartridge on the left for comparison. Centre is a cartridge that had a high pressure load It shows the primer flattened and cratering around where the primer hits the primer.
Right shows a fired factory cartridge for comparison that is at normal operating pressure.
Another way to check for pressure is to measure case head expansion with a micrometer. Use the low powder charge as your datum and compare it to each case as the powder charge increases. .001″ case head expansion above what you got with the minimum charge will indicate a significant pressure increase.
The target below was shot at 442 yards and a standard 30cm rule has been placed onto the target for comparison and scale. The photo shows that as the powder charge is increased, the bullets hit higher on the target. This is to be expected as they are launched at progressively higher velocity and so have less drop over the distance of 442 yards.
The target below shows the results as I increased my powder charge with the 225 grain Hornady SST bullet by 1 grain each time. The bottom hole is the lowest powder charge. The next three are very close to each other in elevation. The top hole is much higher and way out by itself.
To me the three powder charges that groups into a node together provide a clue as to what powder charge to use for best accuracy. These three will be my starting loads when I start shooting groups to check for my best possible accuracy load.
The interesting thing about a ladder test is
that you will notice that this increase in elevation is not constant. Some
loads tend to cluster next to other loads. When they do this it is called an
accuracy ”Node”. You should make note of these powder charges that cluster
because these powder charges are the optimum powder charges for accuracy.
This is important as a small change in powder charge has not made a significant change in point of impact.
Use these powder charges when shooting groups for accuracy. They are likely to give the best accuracy. Powder charges that land bullets out by themselves are less likely to provide the best accuracy as a small change in powder charge has resulted in a large change in the point of impact on the target.
So the ladder test can quickly provide the hand loader with some important information. It provides information on the safe range of powder charges for pressure. It provides a velocity range over the range of powder charges. It also provides an indication of powder charges where nodes indicate the potential for excellent accuracy.
So with only a few shots fired, you are ready to go onto the next stage of load development. Testing for accuracy.