Lazy 30mm question

[moot]

Bullet speed, target speed, same difference: relative velocity's a factor in hitting if we're talking MK108.  E.G. firing a prophub 108 at a 262 running away vs. firing it at a brewster flying almost head-on. On those kind of targets where the time window for a shot is smaller (quicker) than the gun's rate of fire, it does matter what speed the bullets are flying.


Which one lands more hits?
1) bullet stream flying at 2mph
2) bullet stream flying at 2000mph

And for the 108, higher speed means denser bullet cloud for target to fly thru, which means higher probability that it'll connect. 

In my experience, and that's what we oughta be arguing - not just theory with no practical value - the 108 is slow and decelerates enough that it is a factor you can't neglect in making shots.  The running 262's an extreme example, but unless my memory's bad, everyday circumstances are enough for 108 shots that without a doubt are aimed perfectly to not connect because the target flies right thru those gaps.  Solution is either firing shallower angles (superposes more of the bullet stream over target as target crosses it), or tracking the target as you shoot - e.g. with a jink like I did in that long-ish 262 snapshot.
If you're firing from pretty far out where the 108 rounds have slowed way down, it's about as bad as it gets and then you've got not just big gaps due to low ROF, but slow bullets that in the most extreme cases you can literally dodge: e.g. when target's flying so fast that it can see bullets limping along and timing out. You see this all the time e.g. when extending in a 262 with a flock of sprayers 1K back.   

[grizz441]

Which one lands more hits?
1) bullet stream flying at 2mph
2) bullet stream flying at 2000mph

If they fire at the same ROF, then the probability of landing hits will be equal.

Rounds will also deaccelerate at the same rate regardless of their initial velocity and will "fall" at the same rate in the y direction regardless of their initial velocity.  Velocities come into play when we are talking leads, horizontal and vertical, but the basis of this debate was assuming you lead correctly and the target was flying through your perfectly placed rounds.  Clearly bullets with a higher rate of initial velocity are easier to aim with.

[moot]

That blue target isn't stationary.

[kilo2]

I got a golden bullet today....got a kill with the tater at -400....so, like, it's possible, right?

Okay I'm leaving again.  

Hit a tater at 800 before so yes it is possible. Although I do not know the max range of the 30mm.

[grizz441]

That blue target isn't stationary.

Irrelevant, the gaps between the bullets firing at 2mph are very small, the gaps between the 1000mph are very large.

Edit: In your illustratiion the higher velocity rounds will hit with higher probability only because your illustration does not take into account the disparity in the gap size based on the firing velocity.

[SunBat]

If they fire at the same ROF, then the probability of landing hits will be equal.

This is true. The leads must be adjusted but the probablity of hitting should be the same since the lack of velocity is corrected by the close spacing of the slower bullets. It's critical to remember that the leads must be correct in both instances to make a fair comparison.

[moot]

I can't picture it anymore. Gonna have to do it with math.

I think incorrect aim and timing is important to consider in this argument because most people have imperfect aim, esp. with the 108.

Edit: In your illustratiion the higher velocity rounds will hit with higher probability only because your illustration does not take into account the disparity in the gap size based on the firing velocity.

Yes, rate of fire means how long each gap lasts, and varying speed but equal ROF means target should end up with the same amount of time to sneak thru.
But I had something else in mind and now I can't remember what it was.

[grizz441]

I can't picture it anymore. Gonna have to do it with math.

I think incorrect aim and timing is important to consider in this argument because most people have imperfect aim, esp. with the 108.

Yes, rate of fire means how long each gap lasts, and varying speed but equal ROF means target should end up with the same amount of time to sneak thru.
But I had something else in mind and now I can't remember what it was.

You are exactly correct they should be considered for aiming.  This was just a fun silly theoretical debate working under the premise that the bogey is flying through your rounds.  That works off the assumption that the lead and accuracy is perfect.  Actually lead doesn't have to be perfect, it just has to be out in front.  If you are going to error, error on the side of too much lead, as you already know.

[moot]

But lead and accuracy aren't perfect in practice, so it is pertinent for this thread's purpose.. It's in the help forum.

I figured out what bothered me about this.  Bullet speed matters because the target has volume; it's a separate thing from considering gaps between bullets:  If the target has volume, the bullet crossing its path (meaning the volume of space that the target will occupy that coincides with the bullet stream) will take an amount of time directly proportionate to its speed, to cross that volume. IOW the bullet will be present inside that volume which the target has to displace (that coincident volume of target body moving thru bullet stream and volume of bullet stream itself) as it moves thru stream, for longer.

The faster the bullet, the nearer zero the time it takes to cross the target's volume, and the smaller your margin for aiming (not timing) error that's accommodated by the bullet lingering longer in the target's path.  Which is totally counter intuitive.. Reality check says: the faster your bullet (regardless ROF), the less you need to lead, the easier it is to aim and time the shot.

I need to sleep.

[bustr]

Hit a tater at 800 before so yes it is possible. Although I do not know the max range of the 30mm.

135 foot drop at 1000 meters.

If you look at the armorers diagrams in the german manuals, 400 meters was the maximum they concidered effective. That was a 12ft drop at 400 meters. And unlike in AH the motorkanone does not tilt up through the engine as you set the convergence in the hanger to lob over your LOS to perfictly drop your 30mm in the center of your gunsight and offline target. The closest you will ever get with the current gunnery model to the real world motorkanone mounted balistics is to set all of your 109, Ta152, Yak and P39 nose cannon back to 150 yards.

The round dropped straight out of the spinner. The Revi graticule was raised up to see a point on a board 100 meters away 29cm below the 0-datum line of the engine through the spinner. Then you used the bottom stadia mark on the cross hair or the bottom of the circle as your straight line indicator of an impact point 30.745 meters(12ft)  low at 400 meters with the 30mm.

Page 15 shows the screw (21)Hohen which adjusts for the H value in the balistics table for the Visierlinie@100m. It tilts a mirror to raise and lower the graticule.
http://deutscheluftwaffe.de/archiv/Dokumente/ABC/r/Reflexvisiere/Revi%2016%20B%20Waffenhandbuch.pdf

Page 24 for the actual balistics of the 30mm out of a 109 spinner.
http://deutscheluftwaffe.de/archiv/Dokumente/ABC/m/Messerschmitt/Me%20109/Bf%20109%20G-6%20U4%20Bedienungsvorschrift%20-Wa.pdf

By the way the MG151/20 motorkanone dropped 43 inches at 400 meters and 13.6 feet at 710 meters out of the spinner. All guns on the 109's were set to ballisticaly follow the motorkanone to effectivley group the rounds.

[mtnman]

I have to run to work, be back in about 15 hours...

Anyway, a few thoughts-

Bullet stream isn't straight...  This means the gap between the bullets isn't the same size.  They also can't be any closer together in time, so the gap would be closest for two rounds fired while the firing plane is going straight forward with no G's pulled.  That would create a .15 second gap between rounds.

Any change in G's will effect that by making the gap between bullets larger, because it would then be a gap of (time plus space).  Think of a big "S" shaped or "C" shaped shot stream.

Also, the thought of a "stream" is a misnomer.  A stream of 10 rounds is really 10 individually aimed/fired rounds, all of which may be (and probably are) happening under different conditions (G's, bank angle, range, etc).

Lastly, convergence.  What we're looking for with convergence is the best setting for the most circumstances.  Look up "Point blank" sighting-in strategies for sighting in a deer rifle.  That's what you'd want, but applied to the 30mm with a larger target.

[moot]

I have to run to work, be back in about 15 hours...
Any change in G's will effect that by making the gap between bullets larger, because it would then be a gap of (time plus space).  Think of a big "S" shaped or "C" shaped shot stream.

If you can get larger gaps then you can get smaller gaps if target is moving and you aim/time burst just right.

Also, the thought of a "stream" is a misnomer.  A stream of 10 rounds is really 10 individually aimed/fired rounds, all of which may be (and probably are) happening under different conditions (G's, bank angle, range, etc).

Yes but only if they're under those differing conditions.

[grizz441]

I used a larger plane size(remembered incorrectly what ya used) but our numbers are the same mtnman.  Where did Spork go?

[Messiah]

lol @ all this just point and click when it feels good

[The Fugitive]

I think the math was over Spork's 5th grade math.