Suppressed weapons raising bullet arc - POSSIBLE BUG

[TigrisJK 10]

I don't know when this has been happening, since, but my group and I discovered a strange problem with suppressors. Zeroed for the same distance, one would expect suppressed weapons to fire at a lower velocity, and thus lowering point of impact. Contrary to this expectation, they now at a higher point of impact.

http://cloud-4.steampowered.com/ugc/48730002156062824/FCBCCD2F08A522F013488ACBA4E4928F687C603C/ (488 kB)

Here's a test using hynomatic's bullet trajectory module. Weapon setup is a Mk18 ABR with a DMS scope, range to target 600m. Point of aim is the lower edge of the window frame.

The two lower shots, which are on target, were made without a suppressor. The two higher shots were made with the suppressor attached, with the same point of aim. This has been repeated across multiple weapon platforms through many play sessions, and we've finally gotten around to actually testing it.

This is totally weird. Ignore the shot in the center, the new sway put my point of aim slightly off for that shot. Anyway, one would expect a lower velocity from suppressed rounds and for them to drop more, rather than shooting high. If we could get dev comment on this, that would be rad.

Thanks guys.

- Tigris

[Sniperwolf572 758]

It's probably due to the behavior of the zeroing system in Arma combined with suppressors.

Zeroing in Arma adjusts the angle of the bullet when it leaves your rifle. Further away you zero your scope, the bigger the angle at which the bullet exits the gun so you can hit exactly where you're aiming. The calculation of that angle is done by the game automatically depending on the range your zeroing is set to and the rifle/bullet parameters.

One of these things might be happening:

• The zeroing algorithm does account for the suppressor multipliers that alter the muzzle velocity, but the bullet simulation itself does not, resulting in the zeroing algorithm calculating a higher angle than necessary.
  
• The zeroing algorithm doesn't account for the suppressor multiplier and the suppressor increases the muzzle velocity.
  

[CaptainObvious 95]

Anyway, one would expect a lower velocity from suppressed rounds and for them to drop more, rather than shooting high.

While I have no clue why this happens in Arma, look up 'freebore boost' in Google for detail, recap: as suppressors allow the propellant gases to accelerate the bullet a bit more compared to shooting without it, muzzle velocity is slightly greater while suppressor is used.

[martin_lee 33]

I think in ArmA the bullet were slower with suppressor on, that hasn't been changed yet I think. A little bit of blind guesses here: I think the zeroing is recalculated for the slower velocity, so it will have to arc higher. If you look at the green trajectory, the lower one have a slightly higher arc - the path crossed somewhere inside the building. So maybe there is slight error in the range to target measured, causing the slower trajectory to arc high.

Just my guess, though

[CaptainObvious 95]

If you look at the green trajectory, the lower one have a slightly higher arc - the path crossed somewhere inside the building.

If my eyes don't fail me, the bullet traveling the lower line hit barely into the window frame on the backside of the building, hence the steeper curve.

[da12thMonkey 1943]

Anyway, one would expect a lower velocity from suppressed rounds and for them to drop more, rather than shooting high. If we could get dev comment on this, that would be rad.

I think in ArmA the bullet were slower with suppressor on, that hasn't been changed yet I think.

Suppressors used to make bullets slower (~80% of the original initspeed IIRC) but it was ditched because feedback indicated it was a shitty way of trying to make weapons automatically use subsonic ammunition when a suppressor is attached, and suppressors actually have the opposite effect on the muzzle velocity of ammunition (explained by CaptainObvious - freebore boost). Same with suppressors automatically reducing the hit value of the ammunition to represent the lower KE of subsonic rounds. Now if you want to make ammo subsonic you make it a separate magazine - same as everyone did it in previous Arma games.

For a while, suppressors had absolutely zero effect on the ballistic characteristics because BIS set all the coefficients to 1 while they re-evaluated how to implement muzzle attachments in a more realistic manner.

Now by default the ingame suppressors give a 10% increase to initspeed - hence the rounds from a suppressed rifle in the OP travel further, with slightly less severe drop than rounds from a standard barrel. As pointed out already, the slight increase in muzzle velocity is something that occurs IRL, but I doubt it's as big as 10%.

Suppressors also have an effect on the dispersion angle at the muzzle now, so that can also result in observable POI shifts.

Edited July 26, 2014 by da12thMonkey

[blackpixxel 53]

I am just surprised that BI does not simply add subsonic ammunition. We are more than a half year after release now - and they didn't add such a simple thing.

You just have to copy the current ammo and change the initspeed..

[Greenfist 1863]

Yeah, the suppressors increase muzzle velocity which results to a higher impact point at a distance with the correct zeroing. Not exactly a bug in my opinion.

Edited July 26, 2014 by Greenfist