Recoil calculator
Free recoil energy, velocity and impulse, from one conservation law: whatever leaves the muzzle, the arm takes going backwards.
Free recoil energy
8.164 J6.022 ft·lbf
E_recoil = ½ · m_firearm · v_recoil²
- Propellant gas momentum is excluded: ARMAG does not record charge weights (SPEC.md §14). This is therefore a lower bound on the real free recoil, consistent between entries but smaller than a figure that includes the gas term.
- Free recoil: the arm is unrestrained. Stock design, muzzle devices, stance and shooter mass are not modelled, because none of them is a property of the arm.
Recoil velocity
2.046 m/s6.713 fps
v_recoil = p_ejecta / m_firearm
- Propellant gas momentum is excluded: ARMAG does not record charge weights (SPEC.md §14). This is therefore a lower bound on the real free recoil, consistent between entries but smaller than a figure that includes the gas term.
Recoil impulse
7.980 N·s
p = m_bullet · v (impulse = momentum)
- Propellant gas momentum is excluded: ARMAG does not record charge weights (SPEC.md §14). This is therefore a lower bound on the real free recoil, consistent between entries but smaller than a figure that includes the gas term.
What this assumes
- Free recoil is the energy of the arm moving freely, before a shoulder, a grip or a mount absorbs any of it. Felt recoil is a different quantity, depends on the shooter and the stock, and this site does not model it.
- Without a propellant charge the gas term is excluded, so the figure is a stated LOWER BOUND on real free recoil — consistent between entries, and smaller than any figure that includes the gas.
- ARMAG records no charge weights anywhere: they are handloading data, and the editorial policy puts fabrication instructions outside the line. If you supply one here, both it and the gas velocity factor are yours, and no default is chosen for you.
- A muzzle device changes recoil substantially and is not modelled. Its effect depends on the device, and no published figure generalises across them.