Yes - QuickloadPRO offers OBT as a standard feature. You find it in the app as a tab in the calculator:
Optimal Barrel Time (OBT) is a concept in internal ballistics that describes the ideal moment for a projectile to exit a rifle barrel so that accuracy is maximized. We help you calculate the corresponding charges for precision load development (learn more about the concept).
To calculate the OBT nodes and corresponding charges, proceed as follows:
- Create a weapon (/app/weapons) and make sure you enter the correct barrel length.
- Use this weapon in the Standard Calculator to calculate a "Base Load" that matches your requirements.
- Save the Base load in your Load Diary.
- Go to the range, measure your real muzzle velocity with a chronograph, and add the measurement to your load. To do so, go to the Diary, click on the load to open, go to the tab "Velocities", and enter your measurements.
- Once the following criteria are fulfilled, you will see a tab "OBT": Weapon associated, velocity measures entered, and calculated max pressure < 105% of max. allowed pressure, fill rate between 80 and 105%, barrel length > 14 inches.
- On tab OBT, click on the "Calculate OBT Node Loads" button. The app will then automatically do the following:
- Calibrate the powder model to match your measured velocities by adjusting the powder Ba
- Calculate the barrel time (BT) with the adjusted powder Ba
- Determine the two closest nodes, one below, one above
- Determine charges that deliver (with the adjusted Ba) barrel times that match the OBT nodes
- Show the key indicators for these loads
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