The type of gun finally adopted was a muzzle-loading weapon which fired projectiles with external studs which engaged with the rifling. This system was the "Woolwich" system; while it was possible with this system to fire shells at a higher muzzle velocity, and therefore with greater penetrative power, than before, the studs tended to shear, there was excessive wear of the gun liner, and the shells tended to wobble in flight. Furthermore, the muzzle velocity obtainable in these guns was no more than half of that obtained in interrupted screw breeched guns of the following century. There were several reasons for this: the shell could not be made to fit too closely into the bore of the gun, as it would not have been possible to ram it home; the velocity of a shell depends, among other factors, on the length of the gun barrel, and the need to load through the muzzle necessitated a short barrel so as to make the muzzle accessible to the loaders; later types of explosive were superior; and metallurgical techniques improved to allow a higher initial pressure in the breech of the gun.