Match or target hollow-point bullets are designed for precision "target" use and no consideration is given to their expansion or other terminal ballistic performance. The United States military uses open-tip ammunition in some sniper rifles due to its exceptional accuracy. This ammunition is arguably not prohibited by military convention in that the wounds that it produces are similar to full metal jacket ammunition in practice. A hollow-point boat-tail bullet is a match-grade bullet design that uses the concept of a teardrop-shaped tail to give it a lower drag coefficient and make it produce less turbulence in its wake. Only the base of the bullet has a boat tail-like shape – the meplat is still pointed. Some hollow-point boat-tail bullets with longer, more aerodynamic profiles are known as very-low-drag bullets. Terminal ballistics testing of hollow point bullets is generally performed in ballistic gelatin, or some other medium intended to simulate tissue and cause a hollow point bullet to expand. Test results are generally given in terms of expanded diameter, penetration depth, and weight retention. Expanded diameter is an indication of the size of the wound cavity, penetration depth shows if vital organs could be reached by the bullet, and weight retention indicates how much of the bullet mass fragmented and separated from the main body of the bullet. How these factors are interpreted depends on the intended use of the bullet, and there are no universally agreed-upon ideal metrics. Solid lead bullets, when cast from a soft alloy, will often deform and provide some expansion if they hit the target at a high velocity. This, combined with the limited velocity and penetration attainable with muzzleloading firearms, meant there was little need for extra expansion. The first hollow-point bullets were marketed in the late 19th century as "express bullets", and were hollowed out to reduce the bullet's mass and provide higher velocities. In addition to providing increased velocities, the hollow also turned out to provide significant expansion, especially when the bullets were cast in a soft lead alloy. Originally intended for rifles, the popular .32-20, .38-40, and .44-40 calibers could also be fired in revolvers. With the advent of smokeless powder, velocities increased, and bullets got smaller, faster, and lighter. These new bullets (especially in rifles) needed to be jacketed to handle the conditions of firing. The new full metal jacket bullets tended to penetrate straight through a target causing less internal damage than a bullet that expands and stops in its target.