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<300m Zero points are not correct with current bullet trajectory.
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Description

The bullet trajectory is relatively flat out to 300 meters, at which point it starts to drop. True bullet trajectory is an arch.

For example, based on a 6.5x55mm 140 gr cartridge, with a 300 meter zero, the point of impact is roughly 8 inches ABOVE point of aim at 200 meters. (with a 5.56 round its roughly 5 inches, and a .308 is roughly 6)

These bullet physics completely render the reticle on the ARCO useless, as the chevron is designed to give 100 & 200 yard references on the BDC, as well.

Zero distance should also effect your POA/POI.

For example, with a 200m zero, same cartridge, a shot at 100 meters would only be roughly an 2-2.4 inches higher than point of aim. While a shot at 300m would be roughly 9 inches lower than point of aim.

Please incorporate true ballistics trajectory into the engine/game physics.

UPDATE!
Upon further testing there does seem to be some slight POI shift with Sub-300m shots. However, this shift is negligible, and is even more negligible at 100 meters when compared to 200 with the same zero. I have described above how this effects proper use of the ARCO reticle. Please see the picture at this link for the POI/POA for the AGOC/ARCO Chevron reticle: http://pro-patria.us/yahoo_site_admin/assets/images/ACOGReticle.243183548_large.jpg

Details

Legacy ID
1906150465
Severity
Major
Resolution
Open
Reproducibility
Always
Category
Feature Request
Steps To Reproduce

Sight target at 300 meters. Shoot. Observe your point of aim and point of impact. Note that they are the same.
Sight target at 200 meters. Shoot. Observe. Repeat at 100m. Note that POA & POI have relatively little shift. This continues all the way to almost point blank. At point blank there is a height over bore offset, which should be there, as the optics/iron sights are higher than bore.

Additional Information

In the real world, shooters must keep hold over and hold UNDERS in mind when engaging targets, as trajectory is NOT flat out to zero distance.

NOTE: The 6.5x55mm 140gr SWEDISH is NOT the cartridge the game is based upon, obviously. I believe it's probably modeled closer to the 6.5x39 GRENDEL which is a much lighter round. Obviously, my trajectory data should not be used for this purpose in the game. Just used as an example to illustrate my intent in posting this.

Event Timeline

tsmkirbygmailcom edited Additional Information. (Show Details)
tsmkirbygmailcom set Category to Feature Request.
tsmkirbygmailcom set Reproducibility to Always.
tsmkirbygmailcom set Severity to Major.
tsmkirbygmailcom set Resolution to Open.
tsmkirbygmailcom set Legacy ID to 1906150465.May 7 2016, 1:59 PM

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gpha5e added a subscriber: gpha5e.May 7 2016, 1:59 PM

cool! that's what i call good devs! thank you bis

I can't see the issue here. It shoots high at 200m and I'm unable to reproduce a flat trajectory. Has everyone who upvoted this really tested this and found a flat trajectory?

Heruon: I have been told that on certain modded weapons the POA/POI is different and seems to emulate this better (in particular the HK 417 from the R3F pack). However, I JUST tested this using the default guns in the current stable release.

At 100m POI seems to be slightly higher, but not much (about what it should be for 200m. At 200m it is poa/poi. At 300m it is POA/POI, and from here the BDC accounts for accurate drop.

We should be seeing, with a 300m zero, in the case of a 5.56x45 62gr m855, a variance of about 5inches at 200m. This is not reproduced.

Get 200m away from a building. Use windows as a xy axis. Shoot. Move to 300m. Shoot. The poa/poi is almost identical.

The heavier the round, the more drastic the arc. A 6.5mm round would be hitting even higher.

Also note, if the Devs had this implemented they probably would have said so by now stating that I'm crazy.

Whether or not there IS an arch, if there is, it is negligible compared to a true ballistics arc. I should not be able to shoot, and hit a target at 200m in the head poa/poi with a 6.5mm round.

If you truly want to test this, you must use the ARCO. The TIP of the chevron is the 100m mark, Middle is 200m, and center is 300m.

Ok. I'm using default branch and no mods.
The way I test this is by placing units with no ammo and in careless combat mode.
I place them at the airport at 100m, 200m, and 300m.
When shooting a 6.5mm at 200m with POA at the base of the head the bullet misses. Slightly lower and it hits.
I'm unable to reproduce the flat trajectory you've reported, but don't get me wrong I'm not down voting this since I could be wrong.

edit: I've now tested with Opfor weapons, had only tested the MX earlier. The Katiba does seem to have a flatter trajectory.

Heruon: I tested it using the stairs at the airport. At 100m, using the 100m aiming point on the ARCO reticle. I'll aim ABOVE the stair using the proper portion of the chevron, and it hits the stair. I put it at the 300m hashmark, and it goes right where I want it.

I'm not going to say there is NO arch, however, as I stated in the original report... the trajectory is not lined up to the ARCO's reference points, which makes it an absolutely useless optic. Why put an optic in the game, on a set of rifles, which it can't be doped in for?

Either the reticle needs to be reworked, or preferably, they increase the curve of the trajectory to make it match.

I see what you mean now, sorry for mistrusting you :P
But it's really hard to tell if it's the reticle or the trajectory that's bad. Maybe that could be mentioned in the title?

I believe it's honestly a combination of both, but it's honestly hard to tell. Even more so, because the primary round in the game (6.5mm and 6.5mm caseless) is an unknown cartridge with an unknown weight. There's a HUGE difference between the 6.5mm Grendel and the 6.5mm Swedish in terms of trajectory.

However, this is an issue that's been reported since Arma 2 days (see thread here: http://forums.bistudio.com/showthread.php?104715-More-Thermal-Scopes-and-Zeroing&p=1728790&viewfull=1#post1728790 ).

I would also like to see, different trajectories for different caliber bullets, but I don't know how taxing that would be on the game.

I also changed the title to more closely reflect the issue I'm describing.

zGuba added a subscriber: zGuba.May 7 2016, 1:59 PM
zGuba added a comment.May 13 2013, 9:44 PM

For your honesty I did some calculations about 6.5mm Grendel using avaiable sources online - ballistic tables.

Some maths regarding what you can observe in optics:

  • drop at 300 yards: 5.10 MOA compared to 100 yards zero
  • drop at 200 yards: 2.01 MOA compared to 100 yards zero

Representation in angle:
5.10 MOA is 0.085 degree - that's the difference between 100 and 300 yards.
2.01 MOA is 0.0335 degree - that's the difference between 100 and 200 yards.

Vertical Field of View of ARCO optics: 6.507 degrees
Let's say our screen resolution is 1680x1050. 1050 * (0.085/6.507) = ~ 14 px

Now please do following:

Place yourself as NATO marksman (with optics).
Fire 25 rounds out of your 30 round mag while in ARCO optics.
Then, use pause menu console and type setAccTime 0.1, execute.

Fire tracers.

What you observe is tracer flying 10+ pixels above center of reticle, at least on my screen it does so. Proven that, your claim about non-working ballistics isn't valid.

Best regards :)

zGuba, please read all info in the report before commenting. The report is in relation to POA/POI in relation to the ARCO optics and the given references in the BDC.

This said, the 100 and 200m reference points are not accurate to current ballistic trajectory. This has been stated in the initial report, as well as in notes.

Thank you.

Also notice, when determining MOA drop from line of sight, you must be using the same dope on optic. So you can not compare the same line of sight top of an optic at 100 yard zero and 36y/300meter zero.

Please note my post was about 6.5mm ballistics, it's as accurate as it should be.

Haven't noticed the topic changed from its original name meanwhile, but anyway I wasn't talking about sight picture. Sorry if you got me wrong, English isn't my mother tongue :)