Load Development (Ladder Test Method) 

 

First, could you select the specific bullet and Powder you will be using? We do a new selection range here, so you can try different variations to see what your rifle likes.

We always recommend Vihtavouri as a good starting place for most powder uses; they also have a comprehensive website/app for loading data. The ladder test below can be used to find your firearm's preferred primer brand, seating depth and the basis of many more variables. Remember that if any loads misfire, shout your Range Officer or please refer to resources regarding misfiring prior to testing.

 
To find the initial load data to start your testing, find the exact cartridge, projectile brand, weight, and powder combination. If you can't find your projectiles on your powder, you can find the closest weight and use that as a guide parameter.  
When loading your test samples, start at the minimum load and load five identical rounds for each increment (rung), going up by 0.2gr each time.  
Using a chronograph, these should be shot at a minimum of 100 yards, ideally in a stable environment with minimal mirage. Whilst shooting, mark your shots numerically beside each one for reference later. It is also good practice to check for pressure signs on your home loads (flat primers, cratered primers, case head separation, cracking).  

After completing shots, the flat spots in the speeds and the Extreme Spread are the two areas to look at. The first is to find shots that stay around the same rate but differ in weight; these are the flat spots, and you should have two in the entire test. The latter is to look at the difference in vertical height between the shots, those that group tightly together vertically. Combining these two, you will get a sweet spot from which you can take the middle load as the chosen one. The higher load weight in that sweet spot can form a typical hot day with increased pressures, but you are still shooting at the same height. Visa Versa, the lowest, can create a cold day where pressures drop.  
 
Taking this load forward, you can now test the seating depth. For this, you require some equipment to measure accurately: an O.A.L Gauge, a reliable pair of callipers, a calibre-specific insert, a specific modified case, a comparator body and an anvil base to hold the brass. Please also remember that if you are using a magazine, you must adjust lengths to fit that as a priority.  
Set the above items up as pictured on the packaging, and you are ready to get your first measurement. Place one of the same projectiles from above lightly into the neck of the modified case; this should be attached to your O.A.L gauge. If you keep the projectile in the neck, place the gauge into your action, pushing it entirely up to the chamber until the shoulders flush. Depending on the gauge brand, you can now tighten the body so that it does not move whilst you push forward the inner rod. This makes the projectile on until you get resistance if it touches the lands. Screw off the nut to tighten the inner rod; you should be able to remove it all from the action without it moving. Being very careful of your crown, you may find it helpful to get a cleaning rod to push back out the projectile gently.  

Once the gauge and projectiles have been removed, could you place them back in the case and take a complete measurement? Please ensure your callipers are zeroed with the anvil base and comparator body, place the modified case onto the anvil base and slide the comparator body down to get a stable base to measure. With this measurement, you can work up loads; start by taking .02 off that measurement and work up as before in .010 increments. You can then shoot this, measuring the tightest group, similar to the ladder testing. Thus forming the new seating depth. If you want to improve further the longevity of the accuracy of that seating depth measurement, look for individual shots in the testing. Those similar that do not change in the vertical but are seated differently form a group of similarly performing seating depths. In the future, you can use the seating depth measurement with the smallest thou off the lands; when the chambering and bullet jump increase with wear, you will still have up to the highest measurement that you now still shoot the same before you have to retest the loads.