There has been, for as long as the firearms themselves, an argument over what calibers work most effectively in the world of ballistics and defensive firearms. The International Practical Shooting Confederation adopted the Power Factor as a means of evening the playing field in competitive shooting. However, this formula, which multiplies bullet weight by velocity and divides by 1,000, doesn’t take into consideration caliber critical factors in the realm of defensive situations.
A new formula that tries to fill that void is the Defensive Power Factor. The Defensive Power Factor multiplies bullet weight in grains times caliber and times velocity, then divides by 1,000 to come up with a number. This gives a better comparison between different loads. For example, using a 230-grain .45 ACP bullet with 900 feet per second velocity gives a Defensive Power Factor rating of 93.15. This formula goes to prove that caliber is important in a defensive role and leans favorably towards larger calibers paired with heavier bullets.
Such a formula for the DPF also extends to rifles, in which case the divisor is changed to 100. This serves to underline natural differences between rifle and handgun calibers, thus offering a far more accurate comparison within each category. This formula is not perfect, as it leaves out such things as hydrostatic shock, but it is simple to use as a means of evaluating defensive loads.
The .38 Super, along with its 1929 Colt introduction, represents a very interesting case study in ballistic evolution. High velocity and deep penetration were the original design criteria, meant to be used against “auto bandits.” This high-velocity, deep-penetrating round held the superior spot over the 9mm Luger in weight and speed for many years. That is, of course, until one of its number-one proponents became Mexico, then South America, as political forces began exerting influence on regulating military calibers in civilian possession.
Towards the late 1970s and through the 1980s, the .38 Super began to lose some of its popularity due to advancements in 9mm ammo and the new breed of high-capacity “wondernines”. Yes, the .38 Super did find a comfortable niche among competitive shooters who appreciated its propensity to make a “major” power factor with heavy bullets and hot loads. Improvements in barrel design, such as headspace on the case mouth, dramatically enhanced the accuracy of the .38 Super, even more so among competitive shooters.
Although the .38 Super lingers on the edges of mainstream popularity and favor, it is a working option for personal defense with modern jacketed hollow-point ammunition. The debate regarding the best defensive caliber grinds on, but the playing field has been leveled by advancements in bullet design. As one well-known expert observed, “With the proper bullet, any of the major calibers should be fine for defensive purposes.”
The Defensive Power Factor allows a simplistic, easy comparison of various calibers and loads. The heritage of the .38 Super testifies to the fact that truly, ballistic developments have changed with time. It is knowledge of subtlety in ballistics that may spell the difference when it counts, be it for competition shooting or personal defense.