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IDProjectCategoryView StatusDate SubmittedLast Update
0004096USAF[All Projects] Generalpublic2018-04-15 07:152018-04-18 08:34
Assigned Toreyhard 
PlatformOSOS Version
Product Version 
Target VersionFixed in Version 
Summary0004096: 30mm/20mm Cannon Velocity on the AH-64D and AH-1Z is misrepresented to 1/3ish Travel time
DescriptionThe Velocity of the 30mm cannon on Apache takes 1/3ish of the time to get to a target. In reality it has a 800m/s flight time but to go 2400m it took 8 seconds. Compare to the mi24p and the Mi28 30mm cannons which shoot at a high velocity with high rate of fire as well. AS for the 20mm cannon on the AH1Z it is ridiculously under powered and has the same velocity problem as the 30mm. The misrepresentation is horrible and needs to be fixed.
Steps To ReproduceGo into editor (or somewhere to test it) and shoot at targets at various distances.
Additional InformationThe 20mm has a velocity of 1,030 m/s and again to go max range it takes far too long compared to Russian counter parts 23mm
TagsNo tags attached.
Is it a wish/request?No
RHS version
Arma 3 version1.82
Did you used any other mod when the error occurred?Yes
Which mods?Other RHS mods
Attached Files

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-  Notes
reyhard (administrator)
2018-04-15 11:21

Can you link to site stating 8 seconds to 2400m? It's supposed to travel 18 seconds to 3000m so it's quite weird that 600m meters are so ultra slow
VMI18 (reporter)
2018-04-16 00:39
edited on: 2018-04-16 04:52

What is the type of ammo modeled in the mod that the M230 shoots and the M197?
Me and puppy8897 will get a more detailed report as well as finding the statistics on the 2 guns and ammo.

puppy8897 (reporter)
2018-04-16 06:10
edited on: 2018-04-16 06:44

I will now give out some information about the velocity on the 2 guns here.

(M230) In the game, the M230 takes 2.1-2.2 seconds to go 1000M, That is 478 M/s and at 2500M it takes 10 seconds, That is 250 M/s on average. It should go 805 m/s as stated by Orbital ATK, the 30mm ammo provider for the M230 Chain Gun, The M789 HEDP round is stated of having a velocity 805 M/s directly on the website of Orbital ATK as seen here, https://www.orbitalatk.com/defense-systems/armament-systems/30mm/ [^] and in this PDF here. https://www.orbitalatk.com/defense-systems/armament-systems/30mm/docs/LW30mm_Fact_Sheet.pdf [^]

(M197) https://www.orbitalatk.com/defense-systems/armament-systems/20x102mm/docs/20x102mm_Fact_Sheet.pdf [^]
In this PDF the PGU-28A/B is what we have in game, while no velocity is listed in this PDF, it says "The PGU-28A/B SAPHEI provides a superior anti-materiel capability as well as light armor penetration. The projectile is
based on the multipurpose concept with delayed reaction after impact resulting in large fragments and incendiary effects".
I don't think it would acomplish the Semi Armour Peircing affect going 588 M/s out of the barrel.

In the game it takes the 20mm 1.7 seconds to go 1000M, That is 588 M/s, and at 2500M it takes 7.8 seconds, and that is 320 M/s.

It is stated by numerous sources that the volocity should be 1030 M/s

https://www.gd-ots.com/armaments/aircraft-guns-gun-systems/m197/ [^]
https://en.wikipedia.org/wiki/M197_electric_cannon [^]

Now I cannot vouch about how much velocity it loses over time but out of the barrel these rounds should not be acting like they just got fired out of a 2000M long barrel.

reyhard (administrator)
2018-04-16 07:25
edited on: 2018-04-16 08:37

Do you know that air is producing friction?

Also, since you linked wikipedia
"The M789 is typically used in the M230. Each round contains 21.5 g (0.76 oz) of explosive charge sealed in a shaped-charge liner. The liner collapses into an armor-piercing jet of metal that is capable of penetrating more than 2 inches of RHA. Additionally, the shell is also designed to fragment upon impact. The lethal radius against unprotected, standing targets is about 10 ft (3.0 m) under optimum conditions. The M789 requires about 4 seconds to travel 1,000 m (3,300 ft). However, as the shell slows down, it takes over 18 seconds to cover 3,000 m (9,800 ft).[10]"

Seems it should fly slower in game - is it that what you mean?
https://en.wikipedia.org/wiki/M230_chain_gun [^]

puppy8897 (reporter)
2018-04-17 03:56
edited on: 2018-04-17 06:11

I was using Wikipedia to reference the M197 round types and the 1030ish M/s velocity they have, not the M230 Chain Gun. Also the line you quoted from the M230 Wiki here "The M789 requires about 4 seconds to travel 1,000 m (3,300 ft). However, as the shell slows down, it takes over 18 seconds to cover 3,000 m (9,800 ft).[10]" is sourced from https://web.archive.org/web/20100925184129/www.jolly-rogers.com/airpower/ah-64d/64d-arm.htm [^] that lists the velocity as 792 M/s for the gun itself, as well as listing 21.5(g) for the explosive charge even though the data sheet provided by the makers the the M789 HEDP say its 27(g) as seen here https://www.orbitalatk.com/defense-systems/armament-systems/30mm/docs/LW30mm_Fact_Sheet.pdf [^]

As stated by https://web.archive.org/web/20100925184129/www.jolly-rogers.com/airpower/ah-64d/64d-arm.htm [^] it takes 4 seconds to go 1000M. What? 250 M/s on average? That's a loss of 75% of it velocity, with that kind of loss, I highly doubt it would even make it to 2500M even though it is stated that the maximum firing range is 4000M. I would highly doubt the legitimacy of that website that got the (g) of explosive mass and very slightly the velocity wrong.

The Russian 30mm on the Mi-28N is as follows,

3UOF8 HEI - 389(g) - 960 M/s

1000M, 1.0-1.1 seconds, 952.38 M/s
2500M, 3.7 seconds, 675.67 M/s

The American 30mm on the AH-64D is as follows,

M789 HEDP - 339 (g) - 805 M/s

1000M, 2.1-2.2 seconds, 478 M/s
2500M, 10 seconds, 250 M/s

The M789 HEDP (805 M/s) goes 83.85% as fast as the 3UOF8 HEI (960 M/s) but yet takes twice as long for 1000M and 2.7 times as long to go 2500M.

The M789 HEDP (339(g)) is 87.15% as heavy as the 3UOF8 HEI (389(g)) but loses speed twice as fast at 1000M and 2.7 times as fast at 2500M

As you can see, if you scaled up the American 30mm to the Russian 30mm, the percentages would almost match up.

These 2 rounds are almost ballisticly identical in terms of shape, I do not see a reason as to why the M789 HEDP is so much slower than the 3UOF8 HEI.
The M789 should go 83.85% as fast as the 3UOF8 and lose speed slightly faster than the 3UOF8 since its 87.15% as heavy. Since things tend to have a little less drag going past terminal velocity the slower it goes, the M789 HEDP would lose it speed slightly less then that of the faster 3UOF8.

Me and my friend just shot the M789 from 1000M strait up and it took between 2-2.1 seconds to reach the ground, we did this 10 times, all between 2-2.1 seconds. Now, I put a 339(g) projectile going strait down from 1000M WITH air resistance in a calculator, I get a time of fall of 1.24 seconds.

1.24 seconds is how long it should take.
It takes 2.05 seconds.
The M789 is 39.51% slower in game that IRL.

You can watch AH-64D gun cam footage look at the range in the bottom right of the HUD and count the time between shooting and when they hit.
An example of this is this, https://youtu.be/BWsnYxJ1ghA?t=16 [^]
Here you can see the range in the bottom right, 1420M. It then goes away, but you can still get a range by watching the Hellfire hit.
It took 4 seconds from the time the hellfire came off the rails to when it hit, but it did it top down. So with a little bit of calculation, if it went in a strait line, it would take 3.2 seconds.
3.2 seconds with the speed of the hellfire (450M/s) you get 1440M, very close to the lase-range of 1420M.
You can then time how long it takes to shoot and then hit, 2 seconds.
1440/2=720 M/s average speed
I put the same distance (1440) into the free-fall calculator and i get a time of 1.92 seconds, very close to the original 2 seconds it took.

Now on to the M197

PGU-28A/B SAPHEI - 100(g) - 1050-1039 M/s
1000M, 1.7 seconds, 588 M/s
2500M, 7.8 seconds, 320 M/s

I now did the same as the M789 but with the PGU-28A/B, I went 1000M up and it took 1.7 seconds to hit the ground, where this calculator says it should have taken 0.96 seconds WITH drag.

0.96 seconds is how long it should take.
It takes 1.7 seconds.
The PGU-28A/B is 56.47% slower than IRL.

https://www.scribd.com/doc/67289275/20mm-PGU-28-A-B-SAPHEI [^]
https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-28-A-B-F-16.pdf [^]
https://en.wikipedia.org/wiki/M61_Vulcan [^] (The new PGU-28/B round was developed in the mid-1980s. It is a semi-armor-piercing high-explosive incendiary (SAPHEI) round, providing improvements in range, accuracy, and power over the preceding M56A3 HEI round.[9] PGU-28/B is a "low-drag" round designed to reduce in-flight drag and deceleration, and has a slightly increased muzzle velocity of 3,450 feet per second (1,050 m/s))

I never like to link anything to Wikipedia as to say sometimes the sources are garbage, as in the now defunct www.jolly-rogers.com website.

reyhard (administrator)
2018-04-17 09:55
edited on: 2018-04-17 09:55

https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2011/gunmissile/Thursday11800_Nerison.pdf [^]
I agree that Wiki quote seems to be weird (it doesn't even match data from source website) but here you have something more reliable and it seems current ingame performance matches real life performance
2km - ~ 6.6s, it's mentioned that those tracer rounds have slightly higher flight time but I guess real round is close to 6 seconds at 2km too

puppy8897 (reporter)
2018-04-18 08:34

Please allow me some time to gather sources for various things.

Can you please respond about the 20mm M197 problem also.

I am also trying to look up data on the 3UOF8 HEI but am struggling to find sources.

Thank you.

- Issue History
Date Modified Username Field Change
2018-04-15 07:15 VMI18 New Issue
2018-04-15 11:21 reyhard Note Added: 0007648
2018-04-15 11:21 reyhard Assigned To => reyhard
2018-04-15 11:21 reyhard Status new => feedback
2018-04-16 00:39 VMI18 Note Added: 0007658
2018-04-16 00:39 VMI18 Status feedback => new
2018-04-16 04:51 puppy8897 Note Edited: 0007658 View Revisions
2018-04-16 04:52 puppy8897 Note Edited: 0007658 View Revisions
2018-04-16 04:58 puppy8897 Summary 30mm/20mm Cannon Velocity is misrepresented to 1/3ish Travel time => 30mm/20mm Cannon Velocity on the AH-64D and AH-1Z is misrepresented to 1/3ish Travel time
2018-04-16 06:10 puppy8897 Note Added: 0007659
2018-04-16 06:44 puppy8897 Note Edited: 0007659 View Revisions
2018-04-16 07:25 reyhard Note Added: 0007662
2018-04-16 07:25 reyhard Status new => feedback
2018-04-16 08:36 reyhard Note Edited: 0007662 View Revisions
2018-04-16 08:37 reyhard Note Edited: 0007662 View Revisions
2018-04-17 03:56 puppy8897 Note Added: 0007682
2018-04-17 04:09 puppy8897 Note Edited: 0007682 View Revisions
2018-04-17 04:12 puppy8897 Note Edited: 0007682 View Revisions
2018-04-17 06:11 puppy8897 Note Edited: 0007682 View Revisions
2018-04-17 06:11 puppy8897 Note Edited: 0007682 View Revisions
2018-04-17 09:55 reyhard Note Added: 0007686
2018-04-17 09:55 reyhard Note Edited: 0007686 View Revisions
2018-04-18 08:34 puppy8897 Note Added: 0007692

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