My thoughts on the tracer smoke spirals....
At first I thought having any smoke trail was incorrect for the late-war period that AH mostly handles, at least in the MA. I didn't recall seeing any smoke in guncam films from later than about 1941. But with this issue being discussed a lot now, I've gone back and looked at all the film I could find and now see that smoke was indeed visible in most of them--I had just not noticed it before. So, it now becomes a question of how accurately AH2 duplicates it.
I disagree with folks saying the spiral effect is an artifact of vibration, basically a blur effect. This cannot be true because any such blurring would be caused by small, rapid changes in the angle of the camera relative to the line of flight. The effects of such angular changes would be amplified by distance, so things further away would be blurred more than closer things. IOW, if the vibration theory was true, you would see tracer trails as expanding cones getting wider the further away the bullet got, and the target itself would be a large smear. However, this is not the case. In the films (especially late-war films of pretty high quality), the target is often very clear, yet still the tracers going to it have the spiral, which becomes less and less obvious the further away the bullet gets. Thus, it seems that the spiral effect was indeed caused by phosphorous bits being thrown off in different directions as the bullet rotated.
Another bit of evidence in support of the twists in the trail being real things, as opposed to being vibration artifacts, is the observation that trails are more visible when the firing plane is turning. This is because during turns, you're seeing the trails more from above as opposed to mostly end-on. Thus, the kinks in the trail are individually visible against the background, instead of masking each other.
So, AH2's basic idea of having spirals come off tracers is correct, but I think we all agree that it does not look much like what we see in films. AH2's trails look like rail gun trails from Quake 2 or other sci-fi FPS games, being thin, distinct ribbons wrapped around an invisible cylinder about 1 foot wide. OTOH, the trails I see in films are transluscent "solid" cylinders with twisted ridges on the outer surface. They look like ropes made of smoke. If AH2's trails could somehow be made to look more like ropes of smoke than white ribbons wrapped around an invisible cylinder, the overall effect would be much improved.
The only similarity between the film trails and AH2's trails is that the twists in the films have about the same frequency as spirals in AH2. At the Con this summer, HT told me that he based his spiral frequency on the rifling of the real guns. That this closely matches the twists in the film is further evidence that the twisting of the smoke trails in the films was caused by the rotation of the bullet, not the vibration of the camera.
OK, that's it for general appearance. However, there is still the issue of how often the trails should be seen. This seems to me a much more difficult issue. From looking at lots of films from the whole war, trails seem to get less and less common as the war went on. And when seen later in the war, the trails are much less distinct (so that I wasn't noticing them at first). In addition, not all tracers in the same film leave trails, and what trails there are often only cover part of the bullet's path. And sometimes, they only become visible long after the bullet has gone by. However, this is only a general trend--there are many exceptions that seems to do with the caliber of the weapon and its nationality. And in my own experience with 80s-90s US and USSR weapons on the range and in combat, I never saw (or noticed) any trails at all.
It seems to me that as the war went on, there was a general trend toward smokeless tracers. In BoB films, you see scads of trails (8x.303s), but by 44-45 you hardly ever see them and when you do they're usually almost invisible. German films seem to retain the most trails in total, and they're the most visible, throughout the war. This could be due to their use of more and larger cannon than the Allies.
So why are late-war trails so erratic, not being seen for all tracers, nor the full path when present, and sometimes appearing rather late? Perhaps some of this stemmed from manufacturing defects in what were supposed to be smokeless tracer elements. Sometimes, an improperly made element might smoke, or have small areas in it that would smoke, so you'd get occasional trails, sometimes interrupted. The late-appearing trails, however, must be some contrail-like effect, perhaps as water nucleated on ash particles once they'd cooled down sufficiently. I don't know.
