Why does your load data differ from my chronograph measurements?

We are frequently contacted by users who feel the load data deviates too much from other sources or from their real-world results. Please keep the following in mind:

• A deviation of up to 7% is within the expected range of a simulation and is acceptable. The purpose of calculators like ApexLOAD PRO is to help you find starting points for load development faster and with fewer iterations. They do not replace the essential steps of load development, such as fine-tuning via COL and powder variations, and verifying with chronograph measurements.

• In many cases, the input parameters differ from the real application, which is why the calculated results do not match chronograph readings. Most importantly, the brass used often has a different case capacity, and/or the barrel length is not entered into the calculator according to our definition.

• Please contact us in other cases where chrono results differ more than 7% from the calculated results, and we are happy to investigate.

You can log your chronograph measurements in a load diary. This helps us fine-tune our powder models over time by better understanding where they do not yet match sufficiently.

You cannot currently adjust the powder parameters or model yourself to align the calculated results with your measured velocities.