Long Light Bullets (e.g., Spanish CETME and US FABRL) a dead end?

[Essayons]

I want to discuss this, as well. Fascinating concept. I approach it from the angle of trying to get the best external ballistics from mass-produced, hardened steel core general-purpose bullet for something like the 65G.

My concept is a steel arrowhead like M855A1 — but with a longer tail — set into what is, basically, a solid copper "sabot."

I'm not wild about the super light alloys such as aluminum because I'm skeptical of their penetration in general-purpose combat scenarios.

Density of lead is 11.34 g/m3. Density of copper is 8.96. Steel 8.0. Aluminum 2.7 — if memory serves.

Take a look at page 18 of the Frankford Arsenal paper I linked above.

I also agree about penetration or aluminum/plastic cores. The Frankford Arsenal paper shows variations that include steel, lead and even uranium to enhance penetration, though. See pages 17-27 of the linked PDF file.