MG 151/20 Tracers

[bruno_]

As far as I know, two main tracer solutions were developed and used for MG 151/20: a) L'spur (Leucht spur) for daylight-fighting and b) Gl'spur (Glimm spur) for night-fighting. But, I confess, I haven't been able to have a clear understanding about the following points (*):
1) tracer aspect (color of the trails due to light and/or smoke). As to light and/or smoke, an unclear point is if, in the intention of the designers, the tracing function had to be obtained via the light (smoke) and the smoke (light) was just a "secondary by-product".
2) trace space/lenght features (nominal delay(no trace inital distance), if any, and nominal duration/length). May be these features were not unique but a couple of options were available in different times, during the WWII. As to trace length/duration, I 've heard that a "shortened trace" version was developed (at least for L'spur but, maybe, for Gl'spur also): the so called vk. L'spur.

These questions arise also from looking at Luftwaffe guncamera videos (most of them can be found on youtube etc), where, again, a mixed situation can be observed. Sometimes a clear smoke trail can be seen, whereas other movies show just light and, finally, others situations show light+smoke. Since all movies are b&w non clue about colors, of course. Moreover, I don't know if the smoke in the footages is actually smoke or, at least in some situations, is something depending on the altitude, humidity (condensation?) etc. rather than on an intended "design feature" or "design variant" of the tracer.

(*)Before asking I made attempts to see if documented answers to my questions could be found elsewhere.

Thanks in advance for any contribution

 

[Greyman]

Different info from different sources:

20-mm Tracer: bright white, pale green or yellow, 1.8 seconds
20-mm High-Explosive Tracer: bright white, pale green or yellow, 6.0, 1.4 and 2 seconds
20-mm High-Explosive Incendiary Tracer: pale green or yellow, 3.0 seconds

As far as smoke is concerened, when you see thick, white smoke in german guncamera footage I'd assume it was the yellow phosphorous from 7.92 mm API rounds.

A lot of tracers do of course produce smoke.. however, I think this has more to do with certain priming compositions, certain altitudes/locales, and certain chemical impurities than with a reliable, constant plume of smoke emitted from a burning tracer. I have a British test of all sorts of captured italian ammunition and generally it can be seen that brand new tracers (just a few months old) produced a lot of smoke. Tracers that were about three to six (I think, can't remember exact figures.. maybe it was three to twelve or six to twelve...) months old produced no smoke.. and as the tracers aged further than that, they began producing more smoke again.

 

[bruno_]

Hi Greyman thank you!!! Very much appreciated. Both the info and your comments are valuable and make a lot of sense.
Coming back to 20mm, just a "confirmation" question: is the "bright white" referred to L'spur tracers and the "pale green or yellow" to Gl'spur? And "pale green or yellow" means that both variants vere developed and used?
Another point regarding the duration for tracers with three duration options: which kind (if any) of cartridge labelling (words or colours) told the user which variant he had in his hands (normal duration, the shortened version and the long burning one or normal, shortened and ultra shortened)?
Finally, could you tell me something about what the British test you mentioned reports about 7,7mm and 12,7mm italian breda-safat tracers?
Thanks again in advance

 

[Greyman]

Coming back to 20mm, just a "confirmation" question: is the "bright white" referred to L'spur tracers and the "pale green or yellow" to Gl'spur? And "pale green or yellow" means that both variants vere developed and used?

Not entirely sure. Unfortunately I didn't really pay attention to day/night information when collecting. Either both and lumped it all in or just the day info.

Another point regarding the duration for tracers with three duration options: which kind (if any) of cartridge labelling (words or colours) told the user which variant he had in his hands (normal duration, the shortened version and the long burning one or normal, shortened and ultra shortened)?

These aren't necessarily different options, just different figures I have from different sources. Same with the colours. The changes could be standardized changes over time as well.
made-up-example: 6 second white tracers used in 1941, production changing to pale green 2 second trace in 1943

Finally, could you tell me something about what the British test you mentioned reports about 7,7mm and 12,7mm italian breda-safat tracers?
Thanks again in advance

The British were generally unimpressed, but overall approved them for use in British weapons. They were impressed with the 20-mm Breda tracers but in testing their performance seemed very unreliable and inconsistent.

That said it seems to me the British were seldom impressed with the tracers of any other country, so either they were in the lead in that department or they just like they way they did things.

 

[bruno_]

Ok, understood. Thanks again for your answers