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GM6 Lynx 12.7mm 5Rnd Mag bullet trajectory is broken if using zeroing above 1200m.
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Using Hypnomatic's projectile tracing script ( I discovered that bullets from 12.7mm 5Rnd Mag are flying in a very strange trajectories if you set zeroing higher that 1300m. Usage of 12.7mm 5Rnd APDS Mag shows normal projectiles behaviour. More details can be seen in attached screenshot. {F22800}


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Event Timeline

Maxyz edited Steps To Reproduce. (Show Details)Nov 20 2013, 2:18 PM
Maxyz edited Additional Information. (Show Details)
Maxyz set Category to Visual-Weapons.
Maxyz set Reproducibility to Always.
Maxyz set Severity to None.
Maxyz set Resolution to Fixed.
Maxyz set Legacy ID to 407719980.May 7 2016, 5:27 PM
Bohemia added a subscriber: AD2001.Nov 20 2013, 2:18 PM
StJimmy added a subscriber: StJimmy.May 7 2016, 5:27 PM

Probably duplicate of

Though that pic looks hilarious :D

Goose added a subscriber: Goose.May 7 2016, 5:27 PM
Goose added a comment.Nov 20 2013, 4:33 PM

This is due to 2 things:

-first off, 12.7x108mm ammo (non-APDS) has an incorrect airFriction. It is -0.00096, which is the same as 7.62. It should be -0.00055.

This means that at 2000m, it would have bullet drop of about 169m. Compared to APDS, which has bullet drop of about 29m @ 2000m.

You can see the massive difference...

If they used the correct airFriction of about -0.00055, it would have bullet drop of about 70m @ 2000m. Less bullet drop = more accurate zeroing.

The same is true for 12.7x99, it also has airFriction = -0.00096 when it should be about -0.000595.

However, it would probably still be incorrect above, maybe 1600-1800 meters. This is due to...

the second thing, which is that the zeroing "equation" they are using becomes inaccurate at high angles / long ranges.

First things first, change the airFriction on those 12.7x99 and 12.7x108 rounds, then see about fixing zeroing.

12.7x99 = -0.000595
12.7x108 = -0.00055

^these numbers provide velocity in agreement with Soviet firing tables / US data,

Personally I think they should allow manual input of zeroing values (by this I mean, in the weapon config, defining the actual launch angles in radians for different ranges).

zGuba added a subscriber: zGuba.May 7 2016, 5:27 PM
zGuba added a comment.Nov 20 2013, 5:30 PM

Fixed internally

Maxyz added a subscriber: Maxyz.May 7 2016, 5:27 PM
Maxyz added a comment.Nov 20 2013, 5:45 PM

Heh, already fixed. But I gotta say this anyway - basically every weapon shows same results with attached SOS scope. Only this strange behavoiur occurs at different zeroing values - bullets from one of the submachine-guns went straigh to the sky when zeroing was set to 700m.

Goose added a comment.Nov 20 2013, 5:55 PM

"bullets from one of the submachine-guns went straigh to the sky when zeroing was set to 700m. "

Same issue, system becomes inaccurate the more steep the trajectory is - 9x19mm, .45 at 700 meters will have massively curved trajectories, required launch angle will be ca. 9 degrees which means without zeroing, you would have to aim at a point about 110 meters (360 feet!) over the target.

IRL these rounds would never be used at anything even remotely near those distances so I don't consider it a big issue, IMO it would be silly having .45 bullets dropping down on people with perfect accuracy from hundreds of meters.

However when applied to rifles etc with longer intended ranges then it becomes more of a problem.

zGuba added a comment.Nov 20 2013, 9:42 PM

Please think of solution for when flight time exceeds bullet lifetime in your free time. :)

Mmm, not sure I understand... for 7.62mm I think flight time would exceed timeToLive at about 1842 meters.

However I don't know what equations are used to determine launch angle now.

That was message to programmer :)

Goose added a comment.Nov 21 2013, 1:02 AM

Hahahaha :P