 Because the weight of the combined barrel and slide are much greater than the weight of the bullet, the barrel and slide will resist being moved by the inertia of the bullet and thus will move much more slowly in recoil.The bullet will leave the barrel and the pressure will drop to a much lower level after the barrel and slide have recoiled for some distance.The barrel and slide are held together by interlocking grooves that are machined into the top of the breech of the barrel and the inner top surface of the slide.