#Telescoped

In the comments section of my recent Brief Thoughts article regarding caseless ammunition, there was a discussion about whether the cookoff issues of caseless would also be problem for LSAT-style polymer cased telescoped ammunition. Based on conversations I have had with subject matter experts regarding polymer cased ammunition in general, I noted that a lower cookoff threshold is one of the challenges I would expect CT ammunition developers to face. However, after some back-and-forth in the comments, I decided to contact LSAT/CTSAS program officer Kori Phillips regarding this issue (as it was not something I covered in my three-part interview with her), and she kindly agreed to allow her comments on the matter to be published here on TFB. They are below:

Caseless: The ammunition designer’s holy grail, and the engineer’s worst nightmare. It would obsolete the cartridge case overnight, resulting in cheaper, lighter, and more compact ammunition. Weapons would be able to carry 50, 60, or more rounds in slim, inexpensive magazines, and expel them at a rate of fire much higher than current weapons are capable of – not only because the ammunition is lighter and therefore more could be carried to feed such thirsty guns, but because the extraction and ejection cycles of the weapons themselves could be eliminated.

It looks like it could be back to the future for the US Army, if Textron’s new carbine design is any indication of what’s to come. The company unveiled its latest prototype of a cased, telescoped ammunition-firing rifle at Modern Day Marine 2016 in Quantico, VA, on Tuesday. The rifle, which weighs 8.7 pounds unloaded and feeds from a 20-round magazine, is reported to fire a 123gr 6.5mm bullet at 3,000 ft/s, producing 3,350 J and rivaling the existing 7.62 NATO in energy. Military.com’s KitUp! reports:

Previously, we discussed trying to lighten the soldier’s load by making the cartridge case out of different materials, including aluminum and compositing the case out of polymer and metal. Yet, wouldn’t the lightest possible case configuration be… Having no case at all? That’s the thinking behind one of the most ambitious ammunition configurations there is, the case-less round.

Previously in TFB’s series on weapon operating mechanisms, we examined both the closed-bolt blowback system and the open-bolt API blowback system, two very close relatives that share a common feature: Closure of the breech through the inertia of the breechblock mass alone. What this means for small arms designers is that they must engineer a system where the breechblock is large enough to have sufficient mass, while having enough room to reciprocate the distance necessary for reliable ejection and feeding. In a standard submachine gun design using the API blowback system, for example, the breechblock is configured behind the breech end of the barrel, so that it can reciprocate. This is an easy design to engineer, and can be made simply and easily.

The Joint Service Small Arms Program (JSSAP), which includes the program formerly called Lightweight Small Arms Technologies (LSAT) has unveiled a new scaled-up 7.62mm machine gun that fires a larger variant of that program’s cylindrical plastic-cased 7.62mm ammunition. Military.com’s KitUp! reports: