Concept:
Force is defined as the rate of change of momentum:
\[
F = \frac{dp}{dt}
\]
When bullets are fired continuously, the force on the gun is equal to the rate at which momentum is carried away by the bullets.
Step 1: Understand the situation.
Each bullet has mass \(m\) and velocity \(v\). Number of bullets fired per second = \(n\).
Step 2: Momentum of one bullet.
\[
p = mv
\]
Step 3: Total momentum per second.
Since \(n\) bullets are fired per second:
\[
\frac{dp}{dt} = n \times mv
\]
Step 4: Force on the gun.
\[
F = nmv
\]
Step 5: Conclusion.
\[
\boxed{nmv}
\]