###### Ballistics 201: Introducing a New Way of Thinking About Terminal Effectiveness – The Energy Budget

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.

###### Operating Systems 301: What Is Underlug?

Note: In this article, I call this mechanical feature “underlug”. However, this is an error. Several friends of mine and I have been discussing the mechanics of firearms operation for close to a decade now, and we misremembered the term “underslide” from a book by Brassey’s as “underlug”. More details on the error are available in the comments. Regardless, “underslide” is the proper term for this principle, not “underlug”.

###### Operating Systems 301: Introduction to Advanced Concepts

So far we’ve looked at the most basic concepts in firearms operating mechanisms as part of the 101 series of posts, and some more advanced concepts like locking and bolt configuration in the 201 level entries. However, there is a whole lot more depth to the subject, so much that the advanced 301 level discussions will really only be able to scratch the surface. Before we start talking about these subjects though, be forewarned: So far I have avoided including any serious math in the 101 and 201 level posts, but we will have to tackle some math as we delve deeper into how these weapons really work.

###### Operating Systems Omnibus 1: Tilting, Trapping, Recoiling

So far in our exploration of firearms operating systems, we’ve covered ten different mechanisms for locking and actuating an automatic firearm, with two supplementary introduction posts. There’s still a lot more to talk about, but at the request of our readers, I have decided to periodically collect posts together into an omnibus post, so that you the reader can easily access and share them!