Non-incendiary tracers

1. A non-incendiary tracer projectile structure for housing an electrically powered illumination source, the tracer projectile structure comprising:

a jacket comprising a generally pointed forward end and a generally blunt rearward end defining a rear opening;

a protective window that is transparent only to a selected electromagnetic wavelength emitted by the electrically powered illumination source, and

an internal retaining structure disposed towards the rearward end of the jacket to support the protective window, wherein a portion of the rearward end of the jacket tapers in a radially inward direction to define a circumferential narrowing of the rear opening.

2. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure comprises a circumferentially continuous collar on an internal surface of the jacket.

3. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure comprises multiple radially inwardly projecting protrusions.

4. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure comprises a circumferential channel in an internal surface of the jacket.

5. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure comprises multiple circumferential channel portions in an internal surface of the jacket.

6. The non-incendiary tracer projectile structure of claim 5 , wherein the multiple circumferential channel portions are arranged in the same plane.

7. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure is a first internal retaining structure, the tracer projectile structure further comprising a second internal retaining structure disposed towards the rearward end of the jacket, the second internal retaining structure being axially displaced from the first internal retaining structure to define a channel to receive the protective window.

8. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure comprises a circumferentially continuous collar on an internal surface of the jacket.

9. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure comprises multiple radially inwardly projecting protrusions.

10. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure comprises a circumferential channel in an internal surface of the jacket.

11. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure comprises multiple circumferential channel portions in an internal surface of the jacket.

12. The non-incendiary tracer projectile structure of claim 11 , wherein the multiple circumferential channel portions are arranged in the same plane.

13. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure is displaced, in an axial direction, from the first internal retaining structure towards the forward end of the jacket.

14. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure is displaced, in an axial direction, from the first internal retaining structure towards the rear opening.

15. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure is disposed on the portion of the rearward end of the jacket.

16. The non-incendiary tracer projectile structure of claim 1 , wherein the internal retaining structure is disposed forward of, in an axial direction extending from the rearward end to the forward end, the portion of the rearward end of the jacket.

17. The non-incendiary tracer projectile structure of claim 7 , wherein the second internal retaining structure is disposed on the portion of the rearward end of the jacket.

18. The non-incendiary tracer projectile structure of claim 1 , in which the non-incendiary tracer projectile structure is partially provided in a cartridge configured to store a pyrotechnic composition.

19. A non-incendiary tracer projectile structure for housing an electrically powered illumination source, the tracer projectile structure comprising:

a jacket comprising a forward end and a rearward end defining a rear opening;

a protective window within the jacket and that is transparent to a selected electromagnetic wavelength emitted by the electrically powered illumination source;

an internal retaining structure disposed towards the rearward end of the jacket to support the protective window, wherein a portion of the rearward end of the jacket tapers in a radially inward direction to define a circumferential narrowing of the rear opening, wherein the internal retaining structure comprises a circumferential channel in an internal surface of the jacket or a circumferentially continuous collar on an internal surface of the jacket, and the protective window is in the channel or on the collar; and

a seal to adhere the protective window to an inner surface of the jacket.

20. A non-incendiary tracer projectile structure for housing an electrically powered illumination source, the tracer projectile structure comprising:

a jacket comprising a forward end and a rearward end defining a rear opening;

a protective window within the jacket and that is transparent to a selected electromagnetic wavelength emitted by the electrically powered illumination source; and

an internal retaining structure disposed towards the rearward end of the jacket to support the protective window, wherein a portion of the rearward end of the jacket tapers in a radially inward direction to define a circumferential narrowing of the rear opening, wherein the internal retaining structure comprises multiple circumferential channel portions in an internal surface of the jacket, and the protective window is configured with multiple circumferential protrusions arranged to fixedly engage into the multiple channel portions.