What is load development?
Every rifle/barrel is just a bit different, even if produced by the same gunsmith/manufacturer with the same tools. The variables can range of the surface finish of the bore to the microscopic grain of the steel used. Since each rifle/barrel is different, each cartridge should be tailored to the barrel and the needs of the shooter. The key to not burn out a barrel trying to find the perfect load is to use quality components and an efficient load development technique.
What is accuracy?
Every shooting discipline has different definitions of accuracy. Some are looking for 1 hole groups while others lean towards “minute of Man”. The accuracy goal for most practical-style competition shooters is less than 1 M.O.A. (Minute of Angle, roughly 1” @ 100 yards). Due to the speed of shooting, target size, high round count, and the varying weather conditions, shooters are looking to develop a Change Resistant Load. This means your ammunition isn't as dependent on changing heat conditions (weather & chamber temperatures).
Why 10 Shot Ladder Load Development?
Although there are many different techniques to design and test cartridges, the 10 Shot Ladder Load Development was developed to quickly find accuracy nodes through velocity testing. 10 cartridges are loaded to 10 different powder weights and shot over a chronograph to find each velocity. These weights will typically result in a line graph that has velocity plateaus where the velocity changes little from one charge weight to the next. This is referred to as a velocity node and basic idea is “Consistent Velocity = Accuracy”.
Why is velocity so important?
With a consistent velocity, the bullet will leave the barrel and gravity will pull down on the bullet the same amount of time. If the bullet is faster, gravity will have less time to act on the bullet, resulting in a higher impact. If the bullet is slower, gravity will have more time to act on the bullet, resulting in a lower impact.
Where should testing begin?
Begin researching the standards for the cartridge being loaded. Ammunition specifications can be found through SAAMI if they are a standardized cartridge. Determine the Overall length of the cartridge and select a bullet, powder, brass, and primer combination to test. Not all components are created equal; powders burn at different rates, primers have differing amounts of priming compound/cup hardness, bullets have different shapes/weights, and brass has different case capacities and other qualities. Find as many resources about bullets and powders from the manufactures to select the correct components for your application. Check manufacturers websites and reloading manuals to find a starting charge weight and be careful! These are small explosives placed into confined spaces, everything is inherently dangerous. DO NOT start testing based on online forums, videos, and blogs. Start slow and seek more help if you do not understand the complexities of reloading.
What to do after 10 Shot testing?
After testing your 10 cartridges over a chronograph, making sure there are no pressure signs after each round, place these velocities into a graph to see your velocity nodes. Once you have found a node that is in the velocity range you are seeking, you have several options. You can load up 5-10 rounds at a chosen charge weight. Typically, a charge weight in the second half of the node will produce a lower Extreme Spread. Then test those charges, shooting groups to verify the load is accurate as you need.
If you would like to further fine-tune the load, begin testing different Overall Cartridge Lengths. A larger sample size, 5-10 cartridges, will increase your statistical confidence that the cartridge is performing satisfactorily. Start by figuring out your distance to the lands of your rifle bore. An Over All Length Gauge will help to quickly find this length or a more manual method outlined in the Nosler Article below. Next, measure your magazine constraints. There is no use testing cartridges longer than your magazine. Make sure you have plenty of room so the tips of the bullets do not come in contact with the magazine, reducing its reliability. If the overall length of the cartridge touching the lands is less than magazine length, select 5 different seating depths. A quick test is to seat bullets at O.A.L+0.01”, O.A.L-0.02”, O.A.L-0.05”, O.A.L-0.08”, and O.A.L-0.11”.
What is the history of 10 Shot?
Scott Satterlee and the 6.5 guys outline the method to the 10 Shot Ladder Load Development with a blog post and an accompanying video. If you want to dive further into the development of this technique be sure to check both out.