The Pistol Caliber Carbine (Part 1)

The Pistol Caliber Carbine (PCC) is debated in terms of its practical use.  Some view it as a range toy, others include this firearm as part of their survival plan.  In exploring this topic we need to first look at hard data before we can really explore things like philosophy of use.  In Part One of the Pistol Caliber Carbine I will explore the physics involved with this class of firearm versus the conventional SHTF rifle, the AR15.
In Part 2, we will use this data to discuss philosophy of use.
In Part 3, we will talk about common PCCs in Canada.

There are two empirical methods of assessing the terminal performance of a round
1) Kinetic energy
2) Momentum
You can skew the results in favor of your favorite firearm just by selecting a method of measurement that supports the strength of your bullet.  The kinetic energy method holds that a rounds potential is based on the physics formula for kinetic energy where energy is equal to half the mass times velocity squared.  With this measurement method, bullets that go fast are considered superior to those with mass.
On the other end, momentum is based on s simple velocity times mass equation.  People who gravitate towards heavier calibers prefer this method of measurement.
Speaking anecdotally, real world users of light but fast bullets such as HK’s 4.7mm in the MP7, tell about having to expend half a magazine to quickly put someone down.  Similar to this, Delta force operators in Mogadishu found that their heavy hitting 1911s in 45ACP were more effective then their M4 carbines in putting the drug addled Somalis down.
Secondly, if a bullet’s energy expands into an empty body cavity or it exits the body having not transmitted all its energy, then energy kinetic is not an appropriate measurement.
This is why I prefer momentum and will use this as my measurement standard for the following analysis.

In Canada, AR15 users (in an effort to look more cool) seemingly have gravitated towards the 10” barrel on their AR15s.  I don’t know anyone who goes out and shoots anything other than 55grain bullets (except for me) so I will use that as my bullet weight.
Using momentum, the numbers read as follows… 2616fps (797m/s) on a 55 grain (3.56g) projectile.
Final result is 2.837 Newton Seconds.

Out of a handgun, the average 115gr 9mm projectile reads as follows… 1100fps (335m/s) on a 115 grain (7.45g) projectile.
Final result is 2.496 Newton-Seconds.

Out of a pistol, the 9mm is a lot worse than the 10” AR15.

Now if we up the barrel length to 18” on our 9mm PCC to make a non-restricted firearm in Canada our velocity jumps to 1297fps (395m/s)
Final result is 2.942 Neuton-Seconds.

Oh ho!  That is better than the 10” barrel AR15!

How about your standard 230gr (14.90g) 45ACP projectile out of a 18” barrel?
Final result is 4.472 Newton-Seconds.

Wow…. The 45ACP has ballistics like a rainbow with its low speeds but at close ranges, it has an unbeatable punch to it.


Specter Arms sells 14.75” barrel AR15s.  Longer than what is cool but let’s run the numbers on those…
Final result is 3.122 Newton-Seconds.  At this point, the AR15 beats the 9mm PCC but still falls short against the 45ACP PCC.

So the truth is, from a physics perspective, the PCC is just as effective as a AR15 at close ranges.

Now long ranges (100m+) is where the PCC falls down.  This is where we need to look at philosophy of use…  but that is for the next article.