Friday 2010-10-29 Dev. update and Discussion

[Splitter]

Hypothesis:

The "tracer" part of the bullet burns inconsistently. One side burns in essence.

The bullet is spiraling like an American football.

So if only one side of the tracer is "burning", the effect would be the spiral smoke trails we see.

I dunno. Just a thought. I have never seen tracer smoke trails in real life and I am guessing it only occurs on some older ammo. I think the oldest tracer ammo I have fired was from Korea and it certainly was not in .303.

Splitter

[dduff442]

There's a full account of the ballistics of this effect here.

Here are some diagrams from the same source:

http://www.nennstiel-ruprecht.de/bullfly/fig17.htm
http://www.nennstiel-ruprecht.de/bullfly/fig18.htm
http://www.nennstiel-ruprecht.de/bullfly/fig19.htm
http://www.nennstiel-ruprecht.de/bullfly/fig21.htm
http://www.nennstiel-ruprecht.de/bullfly/fig26.htm
http://www.nennstiel-ruprecht.de/bullfly/fig27.htm

The actual helical motion of the round needn't be large (though it can be for some rounds); a yaw angle of 5-7deg combined with the ejection of the tracer gas from the round at speed will exaggerate the effect. Basically, the tracer gas is ejected at an ever-shifting angle to the bullets velocity vector.

The ingenuity some people will exhibit in ignoring the evidence right in front of their eyes is incredible. The spiral pattern in the trace is obvious and unmistakable in any number of guncam clips.

The zig-zag appearance of US tracers is easily explicable as being due to camera shake. Anyone who has any theories about how camera shake could induce a spiral pattern to the tracers while leaving other straight lines, um..., unspiralled is welcome to share them now.

I would argue that this illusion -- previously unknown to photography -- doesn't exist. It's a real, plain, genuine and obvious pheonomenon known to ballistics since the earliest days of rifled weapons and exaggerated by the tracer smoke.

dduff

[The Kraken]

Originally Posted by dduff442

The ingenuity some people will exhibit in ignoring the evidence right in front of their eyes is incredible. The spiral pattern in the trace is obvious and unmistakable in any number of guncam clips.

The zig-zag appearance of US tracers is easily explicable as being due to camera shake. Anyone who has any theories about how camera shake could induce a spiral pattern to the tracers while leaving other straight lines, um..., unspiralled is welcome to share them now.

I would argue that this illusion -- previously unknown to photography -- doesn't exist. It's a real, plain, genuine and obvious pheonomenon known to ballistics since the earliest days of rifled weapons and exaggerated by the tracer smoke.

I don't really see where anyone who argues against the spiral pattern in the smoke. Especially given that this effect is already in Il2 since the very first version. The question is rather if those tracers in the SoW video should be smoking or not.

[dduff442]

Originally Posted by The Kraken

I don't really see where anyone who argues against the spiral pattern in the smoke. Especially given that this effect is already in Il2 since the very first version. The question is rather if those tracers in the SoW video should be smoking or not.

Fair enough.

My guess is that larger calibre ammunition would show the effect more clearly.

dduff