M61A1/M61A2 20mm Gatling Gun Velocity
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Have you noticed one thing about F-16 Gun that is extremely “different” in BMS, especially if you like BFM and tries different platforms sometimes?
I and many others did, so here I’m trying to rise the voice for them and maybe, just maybe, point out something here in this post, which seems to be not “as real as it gets” in BMS, at least in my opinion.
But, hear me out.
I’ve been around flying sims for ages now, but mostly it was/is Falcon BMS, because of the F-16. Recently though other platform bring us almighty Viper so I give it a go and tried it - just to see how it feels.
Btw this thread is not about comparison, we all know what SIM is better and why it is Falcon.
Anyway, first thing I’ve noticed was difference in bullets velocity. They were so damn slow, I was surpriced that I had so many time to react or jink for the upcoming threat, unlike BMS where you feel like dodging star wars laser beam instead. So damn fast boi!
It made me think about real life data, therefore, we did some tests, but before that we looked for rl specifications of the M61A1/M61A2 20mm Gatling Gun Velocity and checked the muzzle velocity,Test conditions:
Both Vipers with the same heading, SAME SPEED!, same altitude, 1 NM separation and spray the guy until out of ammo.
Turns out that in BMS bullets are almost double fast!? 1 NM for a 1.14s!
Now according to rl data it should be almost 2x slower. Right?
Not to mention drag, air density, gravity which should slow it down even more.Is there something that we are missing here or…?
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i DID NOTICE the difference as well, in terms of how deep my “death dot sinks” in the dcs hud with similar speed, distance and Gs circumstances. Gunning in BMS is (always was) a little be “too easy” to be honest. Especially far shooting and G-loaded tracking shots at distance.
the impact of this is what …well, for once encouraged silly BFM choices - as they can be rewarding.
NOte: DCS has different projectiles available for f-16.
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M61A1/M61A2 20mm Gatling Gun Velocity
Should equal the velocity of the aircraft (or other vehicle) carrying it.
Fired projectiles are another matter.
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Should equal the velocity of the aircraft (or other vehicle) carrying it.
Edit: Disregard, now I get it. Better late than ever
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It should actually be the muzzle velocity plus the velocity of the jet…plus the closure velocity times the Tan (?) of the aspect vector. As far as calculating TOF goes.
…or something like that. I’ve slept since then.
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1 nautical mile, taking 1.14s?
1 nautical mile is ~ 1.852 km, so its 1852 m in 1.14 s, or an average of 1625 m/s. If the muzzle velocity is supposed to be around 1030 m/s, that is quite a bit higher than you would expect, although not quite double.
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I’ve been out on a Range watching an aircraft gun fire event from the ground, and it’s a really odd sort of experience - all the sounds are out of order/sequence. First you see the smoke from the muzzle, then you hear and see the rounds whistle in and impact the dirt. Then you hear the burp of the gun actually firing the rounds. All because of the bullets traveling faster than sonic and the distances involved.
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The bullet initial velocity for M61 is set up at 1267 m/s
I will check if code reads correctly and init correctly this value
Note that if you fire at 500kts , that the initial velocity relative to ground will be 1517 m/s already
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If one sim is modeling the M56 rounds and the other PGU-28 you’d expect massive ballistics differences especially at range. Both have similar muzzle velocity, PGU-28 being superior, but at range the M56 is like it has a parachute attached.
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The bullet initial velocity for M61 is set up at 1267 m/s
I will check if code reads correctly and init correctly this value
Thanks for checking it JP! Appreciate.
About the muzzle velocity, Is it supposed to be set for 1030m/s instead of 1267 m/s?Note that if you fire at 500kts , that the initial velocity relative to ground will be 1517 m/s already
That is why we test it in relation to the other plane with the same speed and not to the stationary object in the ground.
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Hi Bruno
I don’t get image loaded where I can see both ac:s speeds.
What was speed that your flying? -
@M79:
Hi Bruno
I don’t get image loaded where I can see both ac:s speeds.
What was speed that your flying?Doesn’t really matter as long as we both kept the same speeds, but if you really need to know ~ 400kts.
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If one sim is modeling the M56 rounds and the other PGU-28 you’d expect massive ballistics differences especially at range. Both have similar muzzle velocity, PGU-28 being superior, but at range the M56 is like it has a parachute attached.
Can you explain this a bit more? what makes the M56 round so draggy?
They both weigh pretty much the same, have very similar muzzle velocities and outwardly look very similar shape wise… So whats the difference?
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I’m not ballistics expert so I could only guess but supersonic dynamics are sensitive to small details.
https://www.gd-ots.com/munitions/medium-caliber-ammunition/20mm-m50-series/
https://www.gd-ots.com/munitions/medium-caliber-ammunition/20mm-x-102-pgu/They aren’t great charts but I did find somewhere that the “in range cue” for F-16 strafe is set at 4000’ for M56 and 8000’ for PGU-28. There’s more to that number than velocity profile (minimum velocity to fuze, effect on target, etc.) but it indicates more than a minor difference.
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The bullet initial velocity for M61 is set up at 1267 m/s
I will check if code reads correctly and init correctly this value
Note that if you fire at 500kts , that the initial velocity relative to ground will be 1517 m/s already
You do this wrt ground speed and not airspeed, correct?
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Can you explain this a bit more? what makes the M56 round so draggy?
They both weigh pretty much the same, have very similar muzzle velocities and outwardly look very similar shape wise… So whats the difference?
It’s not really that they are “draggy” it’s that the bullets are far heavier, so the ballistic drop is much greater. Most target practice ammo (and I seem to recall there is a PGU-28TP round) have solid projectiles, I believe. TP ammo also has a high ricochet probability when fired at hard targets.
M56 (and all HEI ammo) is made from depleted uranium; some API variants feature depleted uranium jackets with a harder/hardened metal penetrator core. What makes depleted uranium a material of choice in such rounds is that it is pyrophoric - i.e.; it ignites and burns due to impact alone and does not require fusing or any additional energetics.
Anyway, it’s the ballistics that matter and there is usually a selection to make the displays reflect whatever is loaded.
https://www.globalsecurity.org/military/systems/munitions/pgu-28.htm
https://www.gd-ots.com/munitions/medium-caliber-ammunition/20mm-m50-series/
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It’s not really that they are “draggy” it’s that the bullets are far heavier, so the ballistic drop is much greater.
Projectile weight:
PGU-28 is 1580 grains = 102.3 grams
M56 is 1565 grains = 101.4 gramsHuh?
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“Sniper shooting” (even without zoom fov) bandits from 1nm+ in super fast jets (MOVING target)… or 0.5nm with heavy G-load… aka “call of duty style”… is not really a real thing … i think. But works too often in BMS. it changes turning-room- and lead- to lag-pursuit-decisions. realism vs gamer-logic …
Try to hit a jet sized target (NOT MOVING target) with a sniper rifle at 1nm (1.8km!!) …and they you get the idea… -
Projectile weight:
PGU-28 is 1580 grains = 102.3 grams
M56 is 1565 grains = 101.4 gramsHuh?
That’s enough difference, given the velocities involved - and when I think of PGU-28 I think TP vs API PGU-28.
There are other factors too…the barrel rotation and bullet spin also affect the ballistics. Way back in another life I had to support some data reduction for GAU ballistics and sight picture presentation. I think the most surprising thing I encountered was the consideration of Magnus Effect on the round - a spinning object actually generates a lift component, and for a bullet that component is magnified as time of flight increases. Relative wind also has an effect on the resultant lift vector and the sum of the two (and gravity) affects deflection from straight path flight.
https://en.wikipedia.org/wiki/Magnus_effect
Plus there is also a lateral velocity component induced by the rotation of the gun barrels (which in the case of what I was working on was selectable high/low rate)…which is also bigger than I might have expected…and again, effect varies with range/TOF. So it’s actually more than just simple ballistics.