#Lethality

In yesterday’s article, we took a look at examples of two different methods of design, which I called “preference-driven” and “process-driven”. For these examples, I supposed two engineers from two different cultures – called “Romulan” and “Vulcan” after the aliens from the Star Trek universe.* In the “Romulan” example, we explored preference-driven design, where a final product is outlined by amalgamating preferred characteristics from previous works to create a desired whole. For the “Vulcan” example, we examined the more elaborate method of developing processes that can be fed data to procedurally generate characteristics as an example of process-driven design.

If you were designing the next small arms round, how would you do it? What methods would you use to determine its physical characteristics and performance attributes? How would you know what was too large or too small, too powerful or too weak? Perhaps more critically, how do different methods for answering these questions compare to one another? Could some methods be better or worse than others?

Today on Modern PDW Calibers we’re going to look at what might seem like a humdrum round, but which represents an important performance band for the modern personal defense weapon. That round is the 5.56x30mm MARS, a purpose built “micro assault rifle” cartridge from Colt designed to fill a similar niche to the WWII-era .30 M1 Carbine.

Today I want to address something that has come up in small arms ammunition development several times in the past 150 years: The small caliber bullet problem. For the sake of this article, I’ll characterize this problem as a perceived trend recognized on several occasions of small caliber (below 0.277″/7mm) cartridges producing wounds that are ineffective at stopping or killing the enemy.

Since we know that gunshot wounds follow physical laws – Newtonian mechanics, specifically – we can use physical quantities to describe what happens to a bullet when it enters a fleshy target. In a previous post, we were introduced to three physical quantities: Force, work, and kinetic energy. To see how these apply to a gunshot, let’s use the example of a hollow point bullet as it impacts and penetrates 10% ballistic gelatin.

One of the primary focuses of my study of modern small arms has been that of their terminal effectiveness, i.e. their “lethality” or “wounding”, although neither of these latter terms are exactly correct. Over the past several years, I have read a good deal of scientific and medical documents, first hand accounts, and treatises by experts, to come to the opinions I have today about the subject; Opinions which – I should note – are still evolving.

Eric’s series on “How Far Will (Insert Caliber/Weapon Here) Kill” has been quite the learning experience. Using a 3/4″ in plyboard as the standard for a potentially lethal wound, even the lowly 22 LR stretches its legs hundreds of yards. Now, Eric and the IV8888 team tackle what might the the hardest to quantify, the shotgun.

The National Defense Industry Association has released the PowerPoint presentations from 2016 Armament Systems Forum, including  Kori Phillips’ update on the Cased Telescoped Small Arms Systems (CTSAS) program, which is the successor to the well-known Lightweight Small Arms Technologies program (LSAT). Of special note in the presentation is the program’s decision to explore (and, to an extent, promote) the 6.5mm caliber as a viable option for CT configuration next-generation ammunition. There is quite a lot that could be discussed about this, but I’d like to focus on two pieces of information given to us by the presentation, those being the effective ranges  and the weight cited for the 6.5mm CT ammunition, shown by the slides below: