#GeneralPurposeCartridge

In three previous articles, we briefly discussed some of the tradeoffs involved in the bullpup concept, and some of the challenges they face in the field of military procurement specifically.  Today, we’re going to continue this deep-dive into the bullpup concept by examining how the selection of either a bullpup or conventional layout affects concurrent development of a new ammunition system. In other words, we are going to address the question: Given the same performance requirements, how does having a longer or shorter barrel affect the characteristics of a new type of ammunition?

We’ve discussed a lot of different rounds in this series so far, but today we’re going to discuss a round that actually has a shot of being adopted (at least in some form) by the United States military as a next-generation small arms ammunition configuration. That round is the .264 USA, developed over the past few years by the Army Marksmanship Unit (AMU).

One thing that seems apparent from the ARDEC presentation on the CTSAS program is the excessive capability and weight of the 6.5mm CT ammunition, as well as its use of lead-cored projectiles as opposed to more modern (and less dense) EPR-type projectiles. Further, the 6.5mm configuration explicitly uses the same case as the 7.62mm CT round, to allow for shorter development times. These facts together indicate that the 6.5mm CT round demonstrated in the ARDEC presentation is not well optimized for minimum weight. For this post, we’ll create an estimate of a new, lighter round that still should be powerful enough to replace both 5.56mm and 7.62mm as a universal caliber. As mentioned in the previous post, we’ll call it the “LW 6.5mm CT” to differentiate it from ARDEC’s 6.5mm CT round.

Recently, I wrote an editorial regarding the LSAT/CTSAS team’s NDIA presentation on their 6.5mm cased telescoped carbine and machine gun concepts. There was a lot to say about the history of Army programs and the pitfalls facing that team, but today I want to get down to brass tacks and explore the weight savings and/or penalty of issuing to the infantry platoon the 6.5mm CT cartridge Phillips’ team proposed. Like in my November of 2013 article on the general purpose cartridge concept, I will be using the loads reported in the paper The Modern Warrior’s Combat Load, released in 2003. That paper is a little dated, unfortunately, but it’s the most comprehensive survey of the platoon’s loadout of which I am aware.

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: