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SD g/mm 2 is the sectional density in grams per square millimeters; m g is the mass of the projectile in grams; d mm is the diameter of the projectile in millimeters; For example, a small arms bullet with a mass of 10.4 grams (160 gr) and having a diameter of 6.70 mm (0.264 in) has a sectional density of: 4 · 10.4 / (π·6.7 2) = 0.295 g/mm 2
Meaning, air density is the generally the same for flat-fire trajectories, thus sectional density is equal to the ballistic coefficient and air density can be dropped. Then as the velocity rises to Bashforth's k {\displaystyle k} for high velocity when C {\displaystyle C} requires the introduction of i {\displaystyle i} .
The light for caliber bullets will transfer energy to a given medium more rapidly, yet with consistent penetration characteristics relative to their sectional density and a constant tapering effect as the bullet graduates to a stop. Such implementations may be conducive to mitigating fragmentation where weight retention is prioritized.
Sectional density is a very important aspect of a projectile or bullet, and is for a round projectile like a bullet the ratio of frontal surface area (half the bullet diameter squared, times pi) to bullet mass. Since, for a given bullet shape, frontal surface increases as the square of the calibre, and mass increases as the cube of the diameter ...
VLD bullets are long and heavy for their diameter, to achieve a high sectional density. [1] Development of VLD bullets has focused on reducing a form factor defined as the sectional density divided by the ballistic coefficient. [2] Form factor can be minimized by: bullet nose design incorporating a secant ogive, tangent ogive, Von Kármán ...
The limit to bore diameter is generally the sectional density of the projectile (see external ballistics). Larger-diameter bullets of the same weight have much more drag, and so they lose energy more quickly after exiting the barrel. In general, most handguns use bullets between .355 (9 mm) and .45 (11.5 mm) caliber, while most rifles generally ...
The 160 gr (10 g) bullet which has a sectional density of 0.328 is similar in sectional density to a 220 gr (14 g) .308 caliber (7.62 mm) bullet. As sectional density plays a large factor in penetration, the .264 caliber (6.5 mm), though a diminutive caliber from a North American point of view, has had excellent results in the field.
Because of the smaller bullet diameter .284 diameter bullets also have higher sectional density than .308 diameter bullets, and because of that better penetration in the target (it takes a 206-grain .308 diameter bullet to get the same sectional density as a 175-grain .284 bullet, an increased weight that requires 15-20% more muzzle energy to ...