Hello dear,

i have listed below solution refer it.

Mass Of Machine Gun(m)= 20kg

Mass of each Bullet, (M)=35g=0.035kg

Velocity Of Bullet(v)=400m/s

No.Of Bullets/sec=400/60=20/3

force = Bullet mass * velocity * rate/second

=0.035 * 400 * 400/60

= 93.333 newton

Hope This Helps.