Ladder Test, Chronograph, Sweet Spot, what is the answer? I have spent the last few months reading everything I could get my hands on regarding tuning a rifle and load development. I spent time at the range trying out a few of the theories and even tried a few short cuts just to see if a non-shooting obsessed person could tune a rifle or develop their best load in a shorter amount of time or with less rounds sent down range.
If you are having trouble sleeping, I recommend mulling over ballistics charts, trying to understand if extreme spread matters or the difference in average or standard deviation. Sounds exciting doesn’t it?
After all of the reading, I did determine how I would develop the load for my rifles moving forward. Before I give you the answers that I came up with, let me lay the ground work for what we are trying to accomplish.
When shooting longer distances, there are variables that are changing constantly. Anything you can do to limit those variables will make your shots better. Essentially, all you are trying to do is make the rifle perform the same every time you pull the trigger.
Thanks to physics we know, in a controlled environment, the distance a 105 grain bullet will fly when pushed out of a 24” barrel with 40 grains of powder behind it. We can measure the muzzle velocity and determine where the bullet will hit down range.
When we start inserting the variables the biggest one is, all powder doesn’t burn exactly the same every time. Your muzzle velocity will be a little different every time. This is going to be a problem when shooting longer distances. If we develop our load to match our rifle, we can try to have a more consistent muzzle velocity and limit how that variable is going to effect your shot.
When developing a load for a rifle there are a few things that stand out. Of course, you can change brands of primers, powder or bullets but let’s look to keep all of those the same and discuss two of the other components..
- Powder Charge
- Seating depth of the bullet
Powder Charge-
Whether you are loading your own ammo or having someone do it for you, you need to get “Load Development Packs.” Copper Creek Cartridge Co. is one of the custom loading companies that offers these development packs. Depending on caliber, the ammo will be loaded with .5 grains difference in each pack of ammo. Copper Creek sells packs of 25 rounds so it is 5 sets.
Time to go to the range!
MAKE SURE AND TAKE YOUR CHRONOGRAPH!!
Ladder Test or Shooting Groups?
I prefer a ladder test first and shooting groups after. Let me take a minute to explain a ladder test.
Disregard windage. Look at your target like rungs on a ladder. Start with the lowest grain bullet. While aiming at the same spot on the target, fire consecutively moving to the next higher loaded round for each shot. Theoretically, your impacts should be lower for the rounds with less powder and higher for the rounds with more powder. Typically you will see a rung in your ladder that has more than one impact.
This is considered the “sweet spot.” This is the the area you want to start looking at for developing your cartridge. Since you took your chronograph to the range too, you also know that this is the area that your shots were close to the same muzzle velocity even though the powder charge was different. If you plotted those shots on a graph they might look like the following:
Before we move on, you should probably have a few more sets of rounds in your development pack. Go ahead and shoot some groups with each pack to see what group patterns the best. It should be a cartridge in the sweet spot that shoots best.
Now that we know where we need to be as far as powder charge, What’s the next step in developing a load?
Seating Depth of the Bullet– Copper Creek Cartridge sells a few tools to assist with measuring your bore. If you have had a custom rifle built, sometimes the info comes with the rifle. I recommend getting the tools anyway and making the measurements yourself. Now, establish another development pack with different seating depths and loaded with your preferred powder charge established earlier.
Each rifle prefers a set amount of “jump” and will react differently by how much the seating depth is adjusted on a cartridge.
Go back to the range and shoot groups again. You will notice tighter groups on the set that has the correct depth set for your rifle.
Now we have Powder Charge and Seating Depth that is close to right. You can stop here or take it one more step. If you want to dial it in one step try loading another development pack with your new established seating depth but adjust the powder with .3 grains of powder in he range of your sweet spot. This time at the range you won’t have to do a ladder test, just stick to 3-5 shot groups. After you have finished at the range, you should know exactly what load your rifle likes.
I know it sounds like a lot, It is actually satisfying when you know you are shooting a cartridge that will consistently be within 10 fps of your optimal muzzle velocity. This will add consistency to your shots and let you start worrying about all of the other variables that come with shooting. Enjoy the new cartridge! (Until you start wearing out that barrel and have to do it all over again!!)