Enter the muzzle velocity (fps) and the barrel twist rate into the Calculator. The calculator will evaluate the Bullet Spin Rate. 

Bullet Spin Rate Formula

BSP = MV*720 / BTR


  • BSP is the Bullet Spin Rate (RPM)
  • MV is the muzzle velocity (fps)
  • BTR is the barrel twist rate

To calculate Bullet Spin Rate, divide 720 by the barrel twist rate, then multiply by the muzzle velocity.

How to Calculate Bullet Spin Rate?

The following steps outline how to calculate the Bullet Spin Rate.

  1. First, determine the muzzle velocity (fps). 
  2. Next, determine the barrel twist rate. 
  3. Next, gather the formula from above = BSP = MV*720 / BTR.
  4. Finally, calculate the Bullet Spin Rate.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

muzzle velocity (fps) = 3000

barrel twist rate = 2.5