Answer:
v = 0.76 [m/s]
Step-by-step explanation:
The linear momentum generated by the shot must be calculated. This can be calculated using the following expression.

where:
P = linear momentum [kg*m/s]
m = mass [kg]
v = velocity [m/s]
![P=0.004*380\\P=1.52[kg*m/s]](https://img.qammunity.org/2021/formulas/physics/high-school/uvskoz90uz19s788uu744ltx0uu5l37ocg.png)
Now we can calculate the recoil velocity, because the momentum is equal for the rifle.
![P=m*v\\v = P/m\\v = 1.52/2\\v = 0.76[m/s]](https://img.qammunity.org/2021/formulas/physics/high-school/ddxrqrhvlh9gtn9jsw0kza4w4jxgh8838a.png)