I’ve seen a few references and photos of an experimental .50 BMG round referred to as LRTA Probe made by AAI in the early 1980s. One photo (from Jestertoo) is below with the round in question on the left.
I have been unable to find any description or details on these, other than the headstamps (LC 81, etc.) and the phrase “LRTA Probe” (nothing specific found on the forum or in HWS vol 3). I understand that LRTA is Limited Range Training Ammunition, however, I question whether this is the correct label for these rounds. The reason is that a similar probe was used on the Trident ballistic missile in the 1970s and referred to as an aerodynamic spike or “aerospike.” The aerospike was used to reduce drag and increase range of the missile, so it would appear to work opposite of “limited range.”
A NASA paper describes development of the spike (emphasis added):
The Aerodynamic Spike (Aerospike) is a deployable drag reducing mechanism stowed within the nose fairing of the Trident I submarine launched ballistic missile. This mechanism maximizes missile performance within the limited envelope available by transforming the aerodynamic characteristics of a blunt, space efficient nose fairing into a more streamlined shape.
This description seems to fit the .50 BMG probe in appearance. Does anyone have any thoughts or information on the development of the AAI round? Could this actually be an experiment to increase range with a blunt ogive?
Below is a depiction of how the aerospike works: