12.7mm MG in Action

[unsobill]

Originally posted by Jippo:

</font><blockquote>quote:</font><hr />Originally posted by unsobill:

</font><blockquote>quote:</font><hr />Originally posted by Jippo:

</font><blockquote>quote:</font><hr />Originally posted by Nidan1:

I thought Soviet tracers were green, are we sure its a 12.7 Russian made or just an M-2?

They're red. </font>

[Jippo]

All of the ones I have seen burnt red, and that is as rare as 7,62x53R and 12,7x108. I have never seen a SU tracer that burned green, although that is not to say that there isn't.

And the tip of the bullet is black violet as in case of API-t (all calibers), green in the case of normal -t. Maybe that is where your idea of green comes from. But if the weapon is NSV or DshK in the video, and the ammunition is API-t I can assure you it is red (burning doh!).

[ June 18, 2007, 02:03 AM: Message edited by: Jippo ]

[unsobill]

you not shooting russian ammo my friend - in Russia we use green tracers with the red tip that burn green - most of the calibers have that including AP rounds.

[Jippo]

Where do the ammunition boxes in the picture come from? What is their color code? What color is their tracer?

[c3k]

Gentlemen,

I have just realized why you two are arguing about the color. You are BOTH correct. Jippo (excellent pictures BTW) says they're red, unsobill claims green. It's obvious from Jippo's pictures TAKEN FROM THE AFT PERSPECTIVE that the tracer's red. That, my friends, is doppler shift. If you were in front, I surmise, the tracer would appear green.

An experiment: I propose a fully filmed experiment in which one protagonist gets shot at while filming the incoming rounds, whilst the other fires and records the results.

Any takers?

(A picture is worth 1,000 words...)

Kem

[Matchstick]

Cos I'm sad I just found out how to calculate this.

As a rough approximation of the velocity needed for a specific red shift can be calculated as

v = ((Lob-Lem)/Lem)*c

where v is the velocity

Lob is the wavelength observed

Leb is the wavelength emitted

and c is the speed of light

Plugging in Lob=510nm (a typical value for red)

Leb=650nm (a typical value for green)

and c=3*10^8m/s

That comes out at about -6.5*10^7m/s which means it would be moving at a little over 20% of the speed of light away from you.

Just a bit more than the muzzle velocity of even a 12.7mm round.

[stikkypixie]

Originally posted by Matchstick:

Cos I'm sad I just found out how to calculate this.

As a rough approximation of the velocity needed for a specific red shift can be calculated as

v = ((Lob-Lem)/Lem)*c

where v is the velocity

Lob is the wavelength observed

Leb is the wavelength emitted

and c is the speed of light

Plugging in Lob=510nm (a typical value for red)

Leb=650nm (a typical value for green)

and c=3*10^8m/s

That comes out at about -6.5*10^7m/s which means it would be moving at a little over 20% of the speed of light away from you.

Just a bit more than the muzzle velocity of even a 12.7mm round.

Shouldn't you be using relativistic formulas for this?

[Jippo]

Oh ****!

[Matchstick]

Originally posted by stikkypixie:

</font><blockquote>quote:</font><hr />Originally posted by Matchstick:

Cos I'm sad I just found out how to calculate this.

As a rough approximation of the velocity needed for a specific red shift can be calculated as

v = ((Lob-Lem)/Lem)*c

where v is the velocity

Lob is the wavelength observed

Leb is the wavelength emitted

and c is the speed of light

Plugging in Lob=510nm (a typical value for red)

Leb=650nm (a typical value for green)

and c=3*10^8m/s

That comes out at about -6.5*10^7m/s which means it would be moving at a little over 20% of the speed of light away from you.

Just a bit more than the muzzle velocity of even a 12.7mm round.

Shouldn't you be using relativistic formulas for this? </font>

[SgtMuhammed]

Its all relative anyway.

[c3k]

Matchstick,

Um, that's all well and good, but you've totally left out the first part: what would the doppler effects be at your postulated .2c on the color green being compressed?

If the TRUE color shifts to red as it travels away from you, then it ALSO shifts towards blue as it approaches you. THAT means the target - call him unsobill for the purposes of this demonstration - sees the compressed/higher energy color. From his vantage it's green. What is the TRUE, zero velocity, color?

Please do the maths and respond (ignore the effects of brane space).

Thanks,

Ken

[Matchstick]

OK, you want the moon on a stick, YOU SHALL HAVE THE MOON ON A STICK

First of all the relativitic equation:

My algebra is pretty rusty by I make (in the above equation) v = 7.1*10^7m/s so about 10% faster than the non-relativistic number.

So now we know how fast it's going we can do the frequency shift in the other direction

Using Lob = sqrt [(c - v)/(c + v)] * Leb again but solving for Lob with v=-7.1*10^7 (negative because it's moving I away)

Lob = approx 830nm which would put it in the near-IR I think.

Just out of curiosity I wondered what this would do to our hypothetical target:

Assuming 60g for a round (http://en.wikipedia.org/wiki/14.5_x_114_mm - no allowance for relativistic mass effect, so sue me) that would give it (using 1/2mass*v^2) 1.4*10^14J of kinetic energy which is the equivalent of 140 Kilotons of TNT. I dont think they would be around to give us their first-hand observeration.

BTW I have had wine with tea tonight so it any of this maths turn out to be completely wrong (and I am fully expecting it to) it's not my fault

[unsobill]

Originally posted by c3k:

Matchstick,

THAT means the target - call him unsobill for the purposes of this demonstration - sees the compressed/higher energy color.

Thanks,

Ken

...im in trouble

[Darius359au]

Originally posted by unsobill:

</font><blockquote>quote:</font><hr />Originally posted by c3k:

Matchstick,

THAT means the target - call him unsobill for the purposes of this demonstration - sees the compressed/higher energy color.

Thanks,

Ken

...im in trouble </font>

[Axel]

Wow, I was thinking of star wars all the time when I saw that?

[Matchstick]

Whoops,

as expected I screwed it up slightly.

I got the wavlengths for red and green the wrong way round.

Red is 650nm and green is 510

DOH !

I've tried the maths again with the correct starting points and (assuming I'm right) it just flips the direction of the velocity round but doesn't change the magnitude so the kinetic energy should be about right (thought with more accurate numbers it may be closer to 150 kilotons of TNT than 140) but it does mean I was completely off with the wavelength (briefly) seen by our unfortunate observer.

I think it should be 400nm which is UV rather than 850nm which is near-IR.

[ June 19, 2007, 01:17 AM: Message edited by: Matchstick ]

[Flanker15]

Not sure what's going on now but here's my knowledge:

Russian tracers are green computer games and WW2 stories in real life they probably use green or red.

The speed required for a substantial Doppler shift in light is well past our capabilities.

[Nidan1]

Jippo,

Was the ammo you fired modern eastern European or Chinese, or some other brand. Military or civilian?

Having been on the receiving end of, and firing Chinese and Sov Bloc small arms back in the day, I can most assuredly state that the tracers were green.

EDIT: I typed this without refreshing...I did not see all this scientific mumbo jumbo, but I can tell you, that from most angles small arms tracers fired from Sov Bloc weapons were green....except on sunny days, but that is another story.

[ June 19, 2007, 07:45 AM: Message edited by: Nidan1 ]

[Jippo]

It was 1980's/90's Soviet stuff. You can see the boxes in the pics. The difference is that I have used almost solely AP-t or API-t, maybe Ball-t is green? I have seen that on few occasions and I should think it was red too, but I may remember it wrong there.

Also I haven't seen SU/WP tracers in smaller calibers than 7,62x53R, but for all I can remember they were red: PKM/PKT, NSV, KPV, all the way up 125mm.

[ June 19, 2007, 09:27 AM: Message edited by: Jippo ]

[Jippo]

Couple of pics just for fun:

[SgtMuhammed]

Big guns are always fun. Well, unless you are downrange.

[Sgt Joch]

nice photos Jippo, what is that tank at the bottom? It looks like a T-62 or T-72, but it's hard to make out from this angle.

[Mikko H.]

T-72. Finnish Army has never had T-62's.

[c3k]

Hmmm,

Jippo's experience may be a cause for concern. Since it seems that all his actual "Russian tracers are red" statements are based on being a FINN.

I postulate the following: real Soviet/Russian/CIS forces use GREEN tracers. The factories which supply export items to, oh, say Finland, are under strict guidelines to CHANGE the color of the tracers. This is obviously needed since any future Russo-Finn war would be confusing because they use similar weapons. Brilliant!

That's how you can tell a Russion T-72 from a Finnish T-72 in combat conditions.

I have solved the conundrum.

Carry on.

Ken

[Nidan1]

Originally posted by c3k:

Hmmm,

Jippo's experience may be a cause for concern. Since it seems that all his actual "Russian tracers are red" statements are based on being a FINN.

I postulate the following: real Soviet/Russian/CIS forces use GREEN tracers. The factories which supply export items to, oh, say Finland, are under strict guidelines to CHANGE the color of the tracers. This is obviously needed since any future Russo-Finn war would be confusing because they use similar weapons. Brilliant!

That's how you can tell a Russion T-72 from a Finnish T-72 in combat conditions.

I have solved the conundrum.

Carry on.

Ken

Don't laugh...you could be absolutely right, maybe the Russians learned from Afghanistan...change the tracer color on all exported munitions to mitigate confusion on any future battlefield.