Physical Review E, "Electrodynamic force law controversy", vol. 63, Issue 5, id. 058602, published 05/2001
the rails need to survive the violence of an accelerating projectile, and heating due to the large currents and friction involved. The recoil force exerted on the rails is equal and opposite to the force propelling the projectile. The seat of the recoil force is still debated. The traditional equations predict that the recoil force acts on the breech of the railgun. Another school of thought invokes Ampère's force law and asserts that it acts along the length of the rails (which is their strongest axis).
CONCLUSION
Recoil forces in EM railguns appear wherever the breech of the railgun is closed electromagnetically. This means recoil forces may appear on power supply
leads, switches, or power supply components themselves.Careful attention is required on the part of the railgun designer to control the location of the
recoil loading and provide means for sustaining the loads. Careless design can result in undesirable forces being applied to the projectile armature as well. On the other hand a thorough understanding of where and how recoil forces are generated can be used to good advantage i n some EM gun systems. In closing we offer aspiring railgun designers one bit of advice originally offered to HPG machine designers by Hr. B. 0. Lamme in 1906, "You can't fool the flux."