Newton’s 3rd law.
Every action has an equal and opposite reaction.
Shoot the gun, and the bike will get pushed in the opposite direction and be hard to control.
The recoil wouldn’t be that bad. Apparently the M1895 was loaded with 6mm Lee Navy at around 2,200J muzzle velocity and a cyclic fire of 450/min. That’s quite manageable. In comparison, the M249 is a shoulder mounted gun of 1,800J, 850/min. That’s 50% more recoil to manage without a bicycle frame to support the firearm.
Ok, but the bike frame isn’t stationary. With a shoulder-mounted weapon you can brace for the recoil with your legs. If you are trying to move forward and shoot at the same time, firing the gun will slow you down. If you try to turn and shoot at the same time, the recoil will push your front wheel in the opposite direction that you are trying to go while your back wheel keeps trying to go forward which is very unstable.
