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"Accuracy vs velocity" Topic


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1,132 hits since 15 Oct 2017
©1994-2017 Bill Armintrout
Comments or corrections?

Garth9916 Oct 2017 6:14 a.m. PST

I may have answered my own question but in regard to WW2 tanks would it be true to say that a high velocity gun would be more accurate than a low velocity gun?

Would there be less of a curvature of drop off over distance with a High Velocity gun?

Andy ONeill16 Oct 2017 6:30 a.m. PST

The accuracy will be pretty similar.
The "drop" will be bigger for a low velocity round meaning distance estimation is more significant.
If you have the time to work out the ranges to markers as you set up then there will be no estimation involved.
Mortars are particularly low velocity but can be very accurate when set up in this way.

A higher velocity is likely to deliver more kinetic energy of course but another significant advantage is vs a moving target.
The faster the round travels, the less time the target has to move somewhere else.

olicana16 Oct 2017 6:54 a.m. PST

link

Gravity has a constant effect. So something travelling horizontally will cover twice the distance, before it drops ten feet, as something travelling at half its speed.

Obviously, ballistics is a little more complicated because velocity drops due other external forces (such as passage through air). In fact, overall ballistics is so complicated (there being so many variables) that, apart from code breaking, its one of the first things military computers were put to work on.

ScottWashburn Sponsoring Member of TMP16 Oct 2017 7:08 a.m. PST

I would imagine the gun sights were calibrated based upon the muzzle velocity of the gun. The accuracy should not be greatly affected unless you are talking about shooting at extreme ranges where the target could move an significant distance between the time the gun was fired and the time the shell arrives.

Personal logo optional field Supporting Member of TMP16 Oct 2017 7:37 a.m. PST

I think this chart (which is for small arms, but still gives a decent idea of how velocity influences drop off) gives a better impression than most verbal statements.
link

You can imagine how much it matters when the gunner aims just "a little high" with a low-velocity round like the .45-70, in comparrison to the same error when firing a higher velocity round like the .308.

It's also worth noting that, due to the greater stress of firing at higher velocities, higher velocity rounds will generally have thicker walls and contain less high-explosive filler. That question of volume can be (somewhat) mitigated by using a longer HE shell of the same diameter. These images of the Soviet 85mm M1939 AT/AAA rounds give a good idea how how much overall volume can vary without altering the diameter.

link

farnox16 Oct 2017 7:55 a.m. PST

Many of WWII apcr and apds rounds were notoriously inaccurate beyond 500 yds even though they were a higher velocity than
standard solid shot.

rmaker16 Oct 2017 9:18 a.m. PST

Another factor is that the higher velocity guns wear out their barrels more quickly.

attilathepun4716 Oct 2017 10:14 a.m. PST

High velocity projectiles drop in velocity very quickly once they exit a gun barrel because the frictional resistance of air increases geometrically to the speed of the projectile. I know it is not s scientifically correct statement, but to put it simplistically, you might say that the harder you try to push a projectile, the harder the air pushes back. Which is why a heavier round of lower muzzle velocity is likely to be more accurate at long range than a lighter one with a higher initial velocity. And, as rmaker just noted, the rifling of high velocity guns wears out faster than that of lower velocity guns. I think the main reason for designing high velocity guns was for greater penetration at average battle ranges.

GildasFacit Sponsoring Member of TMP16 Oct 2017 10:54 a.m. PST

Attila

Correct though your first statement is it isn't really as simple as that and your conclusion is not fully valid.

Resistance varies with many different factors, calibre, shape, even spin rate but, as you say, velocity is the greater factor. BUT – a heavier round will retain a higher proportion of its muzzle energy than a lighter round with range even though it may lose momentum a bit faster.

It is energy at impact that can make a slower, heavier round more effective in some cases than a lighter, faster one.

Accuracy is dependent on some of the factors affecting penetration but not all and there are many more to include that do not affect penetration. Far too complex a system in WW2 for any reasonable predictability function to be derived BUT high muzzle velocity gives a flatter trajectory and so a larger 'error zone' in the vertical plane so, given other factors being similar (and that may be a big if), faster is better for accuracy.

This probably explains one reason why APDS effectiveness drops of quite quickly with range (though doesn't explain why it happens to APCR).

Mark 1 Supporting Member of TMP16 Oct 2017 11:56 a.m. PST

Two topics at play here: technical accuracy (also known as dispersion) and combat accuracy (in gaming circles -- hit probability).

Higher velocity guns are frequently (dare I say generally) LESS accurate, when we discuss technical accuracy. Others have pointed out several contributing factors -- wear on the rifling is one, but there are others. Little mentioned, little appreciated in WW2 but well known in modern gunnery is also the correlation between velocity and barrel length, and the effects of barrel length on accuracy. The longer a barrel is, the more inclined it is to droop or bend. The stresses of firing, the heat induced by firing, and even the heat from the sun over the course of a day can all affect barrel shape, and the longer the barrel, the greater the impact of any variance in barrel shape.

The Germans discovered that their 88L56 was more accurate than their 88L71 over the course of many rounds fired in any one day or any one action. Sure, the higher velocity of the L71 meant that hits could be obtained with greater errors in range estimation, but the barrel tended to troop or bow over the course of a day or with use during an engagement, throwing the rounds down or up vs. the point of aim even when you DID get the range right. Modern tank guns all include a muzzle reference to compensate for barrel droop, but this now-common adjustment was absent from WW2 gunnery.

BUT a heavier round will retain a higher proportion of its muzzle energy than a lighter round with range even though it may lose momentum a bit faster. …

This probably explains one reason why APDS effectiveness drops of quite quickly with range (though doesn't explain why it happens to APCR).

Not quite right. The biggest determinant of loss of velocity is the cross-sectional density of the round -- not so much its weight but rather its weight relative to its diameter. This is what made APDS _more_ effective at range than APCR (or HVAP in US parlance). An APCR round had low cross-sectional density. Both were very light relative to the gun's bore. APCR might have weighed the same as an APDS round, but it was a full diameter projectile, while APDS projectiles, after they shed their sabots, were much smaller than the bore of the gun. So the APDS rounds retained their velocity much more effectively over time (and so over distance).

The problem in WW2 was that APDS rounds were notoriously inaccurate (from a dispersion standpoint). There were several technical reasons, and it took a fair bit of peeling of the onion in post-war development before APDS could get to the levels of accuracy of APCR.

This is why the US didn't adopt an APDS round for its tank guns until the 1960s. The US 90mm guns in the M46/47/48 series stuck with HVAP, and the US didn't transition to APDS until the 105mm M68 gun of the M60 series. Maybe a bit late, as most of the kinks had been worked out by the mid-1950s, but after so many tests with such disappointing APDS results and such good HVAP results, there was a pretty significant bias against APDS that took a lot of proving to overcome.

Or so I have read. Wasn't there doing the tests.

-Mark
(aka: Mk 1)

Mobius16 Oct 2017 12:19 p.m. PST

Accuracy is dependent on two primary factors. One is the individual round to round dispersions. This is caused by difference in cartridge performance and shell interaction with the barrel. It is not directly dependent on velocity and increases with range.

The second factor is as the OP puts it, the velocity. The amount of drop in a set time due to gravity will be dependent on velocity. And because in most cases the range to target is not precisely known the amount of drop to the target will determine if it is hit or not. Thus the less drop the more accurate a shot will be. The projectile does not drop due to air resistance, it drops due to gravity. It slows down due to air resistance and so gravity will have it's influence for an increased time.

Actually Mark, the 88mm/L71 is more accurate than the 88mm/L56 and the longer Panther 75mm/L70 is more accurate (less dispersion) than the 75mm/L48.

goragrad16 Oct 2017 12:27 p.m. PST

Good points Mark.

Although in addition to the sectional density the shape of the projectile also has an impact on air resistance – hence ballistic caps.

As to heat effects, barrel thickness is also a factor in heat effects. A thinner/lighter barrel heats more rapidly impacting accuracy. And longer barrels taper to save weight.

As to erosion, I have read that the RN had tables on their warships that gave velocity and accuracy corrections for the guns based on the number of rounds fired. All based on empirical test data.

Personal logo jdginaz Supporting Member of TMP16 Oct 2017 12:31 p.m. PST

APDS inaccuracy in WWII had to do with problems with sabot separation and the problems with APCR had at least in part due to high cross section versus weight.

Thomas Thomas Supporting Member of TMP16 Oct 2017 1:43 p.m. PST

As noted the Germans did extensive accuracy tests on their own and captured weapons (generally they used weapons that had fired 100 rounds and used "random" ammo).

Jentz has the published results in several of his books. As noted the 8.8L71 and 7.5L70 were the most accurate followed by the 8.8L56 and 7.5L48 and far behind the 7.5L24 (watch out, however, for a misprint in Jentz North African book).

These were real world tests and not theortical musings. As noted the "special rounds" had special problems re accuracy but not due to high velocity.

TomT

Mark 1 Supporting Member of TMP16 Oct 2017 2:03 p.m. PST

Actually Mark, the 88mm/L71 is more accurate than the 88mm/L56 and the longer Panther 75mm/L70 is more accurate (less dispersion) than the 75mm/L48.

Mobius, that's true for the first shot, at 10:00am.

But it is not true for the 20th or 30th shot in a given engagement, or at 3:00pm on a sunny day.

This was the issue that confounded the Tiger II crews. Their guns became less accurate over the course of an engagement, or over the course of a day. Even a cold day (maybe even in particular during a cold day), if it was sunny. The top of the barrel heats up, the bottom stays cold, the top expands, the bottom doesn't, the barrel bows and the gun throws the rounds all around your aim point.

We know how this works today. We put on barrel shrouds to even out the heating from firing, and to protect the top of the barrel from solar heating, and we put a muzzle reference to recalculate the zero continuously with each round fired. And we never build guns longer than L62, because that was determined to be the magic point beyond which more barrel just meant a slower round (more friction, not enough propulsion) and more dispersion.

-Mark

Mobius16 Oct 2017 4:27 p.m. PST

Mark do you have any documentation other than anecdotes? How many Tiger II engagements were the crews confounded by barrel warp?

Lion in the Stars16 Oct 2017 5:23 p.m. PST

Just as with rifle shooting, velocity matters because it reduces range estimation error and wind estimation error (the two biggest sources of misses in rifle shooting at long range).

As optional field's link shows, there can be an enormous difference in trajectory between a slow slug and a fast one (.308 is roughly 75% faster than .45-70).

Also factoring into the really extreme difference in trajectories between .45-70 and .308 is bullet shape. A good comparison would be the 6.5 Carcano versus the 6.5 Arisaka. They're both 6.5mm slugs, weight within 15% of each other, and have about the same muzzle velocity. But the Carcano uses a round-nose slug which slows down very quickly (subsonic at about 300m), while the Arisaka has a spitzer bullet that is much more aerodynamic (subsonic at 1200m).

RudyNelson16 Oct 2017 5:37 p.m. PST

As others may have pointed out, accuracy is a matter for sighting systems. A low velocity gun using a ghost sight will be more accurate than a high velocity gun using a V sight.

As I have pointed out before, the 1976 Tank Gunnary manual stated that a Sherman 76mm gun using a V sight firing at a stationary target ONLY 500 yards distant needed 13 shots before a hit chance reaches 50 percent.

badger2216 Oct 2017 6:43 p.m. PST

Another problem with long tubes is something I was taught is sometimes called muzzle whip. I am sure there is a more technical term for it, but I dont know what it is.

Basically as a projo travels down the barrel it causes the tube to vibrate. On most tubes it is so small it is not a factor. The tube I am aware of that it did cause trouble was the US 175mm howitzer( M107 I think). The 175 was a very long tube with high velocity( for a howitzer) and was intended as a long range weapon. As dispersion is an angle, the farther you shoot the greater the dispersion (we call it probable error). So at the long range of the 175 it got to unacceptable levels. And muzzle whip was determined to be one of the major contributing factors. So it was withdrawn from US service. By the time I was in long enough to understand the idea, it was no longer with us.

Mark1 and Mobus are both going to want references on this. I dont have them. I learned a little about it in AIT, and a little in BNCOC. Neither covered it very much as it was not in the inventory. Mostly I learned because one afternoon in Graf we were parked next to a brit battery who were still using them. My BN FDC chief had served in a 175 batteryand spent some time explaining to me what they were goood for and and shy we did not still have them. And, other than really long thin gun tubes it probably doesnt matter.

Artillery also records ever round a given tube has fired, and its charge and can use that to determine expected MV lose. We prefer chronographs, but those are not always available or working. What I always found interesting was that for some shell/propellent combinations on a given gun the numbers could be close, but on a different combination on the same gun they would be a lot different.

Owen

goragrad16 Oct 2017 10:24 p.m. PST

Ah, barrel whip.

Twould be interesting to see some high speed films of some of those high caliber guns firing. Particularly one like that 175mm gun on the M-107.

At least in the rifle world the long thin barrel can get quite whippy – PSL-54cs are notorious for it. They are also very susceptible to heating – fire a clip in rapid succession and the vertical stringing is significant.

The older sniper rifles had bull barrels just as target rifles (and pistols) do to reduce both of those factors.

Without having been in an artillery unit or around one, I would presume something similar occurs.

Mobius17 Oct 2017 5:47 a.m. PST

This report has a table list of various deviations caused by factors on page 19.
link

Thomas Thomas Supporting Member of TMP17 Oct 2017 8:27 a.m. PST

The difference in accuracy between low and high velocity guns is sufficient that it should be modeled on wargames tables. At short range it makes no difference but at long range it does, hence impacting tactical (ie player) decisions. (Complex modeling of tech that does not impact player decisions should be avoided.)

If you want to add the complexity of "warm" barrels than you would also have to compensate for the tendency of tankers to hide in shady places, the cool weather in most of northern Europe and that ammo limits limited continuous shooting. The effect might be to somewhat limit the differences but to elminate them is to go way too far.

Qualtiy of sights is a seperate matter. We can assume for the question of high v. low velocity accuracy that all other factors are equal. If there is a large gap in sight quality that would have to be modeled as a seperate question. It seems, however, with high velocity guns the incentive was to provide adequate sights so the two factors often compliment rather than negate each other.

TomT

Murvihill17 Oct 2017 8:59 a.m. PST

"In fact, overall ballistics is so complicated (there being so many variables) that, apart from code breaking, its one of the first things military computers were put to work on."
I think the first thing military computers were put to work on was stellar navigation tables.

Blutarski17 Oct 2017 9:43 a.m. PST

The devil is always in the details naval gunnery dealt with "cold gun" corrections for the initial round; more important was accounting for the "error of the day" wind velocity/direction, barometric pressure. Of course, the shorter the range, the less influential were these factors.

The most important fundamental advantage of a high velocity weapon IMO was flatness of trajectory. Taking the 88mm Flak 18/36 as an example -

Range 500m
Angle of Fall 0.1875 deg
Danger Space (3m tall target) 916m*
* at 500m, the maximum ordinate of the trajectory was only 2m

Range 1000m
Angle of Fall 0.5000 deg
Danger Space (3m tall target) 343m

Range 1500m
Angle of Fall 0.8125 deg
Danger Space (3m tall target) 212m

Range 2000m
Angle of Fall 1.1250 deg
Danger Space (3m tall target) 153m

Range 2500m
Angle of Fall 1.5000 deg
Danger Space (3m tall target) 115m

Technically speaking, at ranges < 1500m, the danger space was sufficiently ample to allow for the expected average 20pct error associated with unaided (eye) range estimates.

- -

While on the subject of the Flak 18/36, here are the mean dispersion characteristics (i.e., the bounded vertical rectangle (H x W) within which 50pct of the shot fired would be statistically expected to strike at the specified range).

Range 500m
Mean dispersion 0.3m x 0.2m

Range 1000m
Mean dispersion 0.7m x 0.4m

Range 1500m
Mean dispersion 1.1m x 0.6m

Range 2000m
Mean dispersion 1.6m x 0.8m

Range 2500m
Mean dispersion 2.1m x 1.0m

- -

To be sure, the above data do not allow for pointer error, which was the dominant factor influencing battlefield weapon effectiveness. But, if the Flak 18/36 can be taken as more or less representative, the above figures do imply that such guns were quite accurate technical instruments in and of themselves.


B

Wolfhag Supporting Member of TMP17 Oct 2017 12:18 p.m. PST

I agree, flatness of trajectory is most important when firing at targets that have a vertical profile. However, if firing at a target on the ground like infantry and dug in positions, a lower velocity will give a higher trajectory and a smaller danger space. This is why the Germans used the 75L24 for their infantry support. Lower velocity shells do not need a thick casing allowing space for more HE. High-velocity guns have a smaller HE charge and larger danger space. When you miss a ground target the higher velocity shell will travel further than a lower velocity shell.

the 75L24 has a muzzle velocity of about 385 m/s which means about 50% of the danger space of the German 88 which is 810 m/s. That translates to less dispersion on the ground and larger dispersion against vertical targets like tanks. This is the reason the US 75mm gun on the Sherman gave better results against ground targets, better than the higher velocity German guns and the 76mm gun.

This is also why mortars can be so accurate too.

There are other factors like the height above or below the target of the shooter but I doubt if you can really translate that into a game.

Wolfhag

goragrad17 Oct 2017 3:31 p.m. PST

Good points Wolfhag. As a bit of a tangent noting why infantry guns remained in service throughout the war – mortars can be accurate enough to drop a round down a chimney, but an IG can put a round through the ground floor (or higher) window of a multistory building.

As to barrel heat as a factor, few engagements may have been as intense as Beda Fomm, but at lest one history I read noted that the firing was so rapid that the barrels of the guns of some of the British tanks were noticeably drooping.

Wolfhag Supporting Member of TMP17 Oct 2017 7:02 p.m. PST

My approach for direct HE fire at ground targets is to determine how far ahead or behind of the target the round lands if it misses. This takes care of near misses and adjacent targets being damaged.

Anyone else going in that direction?

Wolfhag

UshCha Supporting Member of TMP17 Oct 2017 10:55 p.m. PST

wolfhag, we have a danger zone which increases with range in line of flight but currently none normal to the gun. Not perfect but as can bee seen the error normal to the gun ( horizontal) is less and I am all for simple if you can get away with it.

Andy ONeill18 Oct 2017 1:07 a.m. PST

@Wolfhag
For direct fire I count a miss as zero effect. We've tried the round must go somewhere approach but it was considered a step too far towards reality by players.
For indirect fire, I use dispersion and area.
We have less indirect fire in the games.

I've long vacillated over changing he effect from a template to an abstracted effect.
I like simple.
My players like simple.

Mobius18 Oct 2017 4:06 a.m. PST

Wolfhag, for HE I just have a beaten area that has a longer axis in the direction of fire.
For direct fire of base eject smoke I have a random distance from the aim point that the smoke will form. Because the round can skip after it hits.

Lion in the Stars19 Oct 2017 2:02 a.m. PST

For most of the different settings I game, hit or miss is good enough.

For Infinity (28mm scifi, 1 fig=1man, and telescoping ground scale), though, sometimes it's important to know where exactly that explosion actually landed.

Wolfhag Supporting Member of TMP20 Oct 2017 8:26 a.m. PST

Lion,
I agree it is more applicable to 28mm scale, especially in an urban environment.

Mobius,
That's the approach I'm taking. In my detailed gunnery routine, I plot the MPI result of the shot against the target's image in .1 meter increments so I can see how far above the ground or in front of the target the round missed. By knowing the AOD I can determine how approximately how far the round will travel and land in front or beyond the target for each 0.1 meter it missed.

According to my right angle calculator, an AOD of 0.5 degrees will travel about 11 meters for every 0.1 meters it is above the ground. My gunnery charts are in 100-meter increments already so having the value pre-computed it's just a matter of adding an additional row to the chart, no player calculations needed for that.

I know it's not perfect as the AOD will increase every 100 meters but for game purposes using a scale of 1 inch = 25 meters, it's a quick solution.

It is also a quick method to determine the results of a bounced HE round creating an air burst. A Sherman 75mm HE round hitting below (short of the target) the image of an anti-tank gun will travel about 25-35 meters with a delay of 0.05 seconds depending on the range. That means an air burst would affect an anti-tank gun or infantry if the MPI result of the shot was 0.1 or 0.2 meters below (25-35 meters horizontally in front) the image of the anti-tank gun or infantry target. I have not run this by anyone else so I'm open to suggestions and corrections.

You would not necessarily need to use the method of determining the MPI over the target image. If a round misses on an odd number the round was too high to have an effect. If the roll was an even number it was short and may have a blast effect.

Just to be clear, I'm not attempting to plot exactly where every round fired lands to the nearest 1 meter, that's ludicrous. I'm just trying to get a more physical model of the results of a direct fire shot (not mortars) aimed at a point on the ground rather than using random abstractions. Like Andy O'Neal said, it's not going to matter for the majority of the shots and I agree. I think with the method I've outlined you could tell very quickly if it will matter or not without additional rules, templates or die rolls.

Wolfhag

Mobius20 Oct 2017 8:47 a.m. PST

Wolfhag, you have to remember a HE shell hitting a near 0 horizontal will have a weird blast pattern. It spreads out perpendicular to the shell path but not far long the path.
Abstraction of the random MPI along with the blast pattern might be a hit probability hit box.

link

Andy ONeill20 Oct 2017 10:38 a.m. PST

@Wolfhag.
I dunno mate.
Every time you talk about any mechanics you bring on that science stuff.
You're probably right and it sounds like how reality works.
It all sounds a bit hard to me though.

My advice.
Don't directly model reality.
Model the effects.
Simpler.
Still simpler than you're thinking.

If you really want to have the chance of hitting another target then come up with something very very simple.
If you're within n and roughly in line ( or some hand-waving-ness ) then you roll a dice per "near" unit.
They're hit on a 1.
Ignore this completely for calibres under …..
The bigger the bang then the smaller the dice rolled.

Do your super science and graphs. Work out roughly the right shape and distance and stick that in your designer notes where players can read it and be reassured you used some real world stuff on this.

UshCha Supporting Member of TMP20 Oct 2017 12:34 p.m. PST

The link was very interesting. In most games you would be aiming only for Neutralization. To do 30% damage would need about 690 rounds on a 100 yd square area. That is an enormous quantity and would not be available for many targets, and would need a massive stockpile of ammo. Typically a pltoon will cover about 250 by 100 yds so you would need 1700 off 25 pounder rounds. That would take a battery of 4 off 25 pounders around 43 minutes to fire if the continuous rate is 10 rounds a minute which may be generous. Our own data was based on a number of US modern manuals available to the public do not vary massively with these sources.

Plotting individual rounds is not very productive, nor is modern fire effects based on this. You decide what the target is, what the terrain is and the area. Look up the table to get a figure for that target/terrain and divide that into the area to get the number of rounds. We simplify a bit but its essentially based on those values. Working out the "danger Close" is harder. we use 200m which is about reasonable for close in artillery but is well out for long range artillery working towards the limit of its range (it can be 500m)

Lion in the Stars20 Oct 2017 2:24 p.m. PST

Yeah, as I understand modern HE usage, the idea is to spread shell fragments across an area, you fire enough shells to cover the area (allowing for dispersion, etc). But you're only going to kill troops in the open on the first few rounds arriving, after about the second round everyone will be prone and complaining about their buttons keeping them from getting closer to the ground.

But dropping HE on a platoon that is dug in will only keep them from moving or shooting very effectively (it's one of the things that I really like about Flames of War, hit a platoon with a bombardment and they're pinned).

UshCha's point about Danger Close is the primary reason for GPS-guided artillery and mortars. The M549A1 155mm shells have a 267m CEP at max range (that is, only 50% of all shells fired at the target point will land within 267m of it!), which means that artillery needs to be much closer to the requesting troops in order to drop rounds close to them 'safely'.

If you put an M1156 guidance module in a standard 155mm shell, the CEP tightens up to about 15m. If you use an M982 Excalibur round instead of the GPS-guided fuze, you get 5m CEP (and a lot longer range).

This puts Danger-Close for 155mm guns to within 150m of Friendly forces!

Wolfhag Supporting Member of TMP20 Oct 2017 3:34 p.m. PST

I have a friend that was a Company Commander in Vietnam. When calling in 8" arty he had to be at least a mile away.

Plotting individual arty rounds is annoying but most players find it entertaining in 28mm.

That arty link Mobius posted is probably the best single source for artillery data and tactics I've found. The sheafs are really kidney-shaped, not pie plates. I saw a video of direct fire air bursts and you could see the shrapnel hit the ground in a linear pattern perpendicular to the gun.

Wolfhag

badger2220 Oct 2017 4:35 p.m. PST

wolfhag my sheaf is what shape I want it to be, depending on how much time I want to waste messing with it.

Of course most of the time you have a standard and just shoot that. But the shape changes as you get away from the azimuth of lay and the shape of the guns on the ground changes in relation to the azimuth of fire.

Modern fire control computers automatically calculate individual guns into a circular sheaf of course, and then variation warps it a bit.

I am interested in your rules, to bad you dont make it all the way north to WA to demo them.

I shot cannons for 21 years, you ever have a question an FDC NCO should be able to answer, ask away, I still love talking about this Bleeped text

Owen

Wolfhag Supporting Member of TMP20 Oct 2017 4:55 p.m. PST

Badger,
You're on, send me an e-mail at treadheadgames AT gmail.com and I'll get you in the loop.

I have pdf's of dozens of issues of Field Artillery Journal, Field Artillery, Artillery Trends, and manuals. I'm only doing WWII for now.

I went through Recon training which also involved FO. My fantasy was to be by the DMZ with the USS New Jersey on my net ready for a fire mission. Sadly, it still remains a fantasy as we've both been decommissioned.

I'm in the SF bay area, no plans for WA for now.

Wolfhag

badger2220 Oct 2017 5:45 p.m. PST

Enfilade, on memorial day weekend is the largest historical minis con on the west coast. Yes a long way to go, but I can hope. I also periodically bug Rich Clarke of TFL to come over and that is a bit more. No luck there yet either.

badger2220 Oct 2017 5:56 p.m. PST

Hope I can help.

Many years ago, I had a retired LTC come to my FDC track. He had been in our BN in WWII as a fire direction officer and wanted to see what all the new stuff was. Our BN XO brought him to me as I was kind of a Manuel fire direction freak( computer can go down, have to kill the people to stop them). After I showed the old guy the computer and stuff, we started pulling out our Manuel gear. With a little bit of refresher, he could have sat in and fired missions. Our charts and darts had not changed since WWII. Now certainly a lot was different, the tape things they used where long gone,but a lot was still there.

Long winded way of saying while I am not that old, I do have some insight into WWII artillery'


Owen

uglyfatbloke Supporting Member of TMP21 Oct 2017 9:30 a.m. PST

Once again, I'm indebted to you all for extending my education; much obliged!

Wolfhag Supporting Member of TMP22 Oct 2017 10:45 a.m. PST

Garth,
A fairly simple way to reflect accuracy and velocity in a game is to index the accuracy values in 0.5 second time of flight increments.

Example: German 88L71 MV: 1000m/s
Range 500 1000 1400 1800 2300 2600
ToF 0.5 1.0 1.5 2.0 2.5 3.0
Accuracy 95% 90% 85% 70% 55% 35%

Example: Russian 85L52 MV: 792m/s
Range 400 800 1150 1450 1800 2050
ToF 0.5 1.0 1.5 2.0 2.5 3.0
Accuracy 95% 90% 85% 70% 55% 35%

Don't hold me the accuracy value percentages, it's just an estimation. You could use artificial terms for the range like short, medium. long, etc. to replace the ToF value.

Wolfhag

Mobius22 Oct 2017 11:27 a.m. PST

I prefer to drop the accuracy in 10% increments so one can see the sinusoidal nature of the ballistics.
It is not unlike larger divisions like point blank, short, medium, long, extreme, but more of them.
Example: German 88L71 MV: 1000m/s Target:T-34/76, Sight:TZF-9
Range m: 520 650 800 920 1050 1180 1350 1570 1900 2550
Accuracy: 95% 90% 80% 70% 60% 50% 40% 30% 20% 10%

Example: Russian 122 D-25T AP 781m/s Target: PZIV, Sight:TSH-17
Range m: 420 520 640 730 830 930 1050 1210 1440 1880
Accuracy: 95% 90% 80% 70% 60% 50% 40% 30% 20% 10%

Wolfhag Supporting Member of TMP23 Oct 2017 12:13 p.m. PST

Mobius,
I prefer the D20 and ranges rounded to 100m.

If Garth99 liked your gunnery tables is there any chance you would happen to have them already done for most of the US, Soviet, German and Italian tanks and guns?

Wolfhag

Mobius23 Oct 2017 12:37 p.m. PST

I don't have any current tables made up. Panzer War firing tables are a bit dated as they don't reflect my current sighting system and more recent research.

My tables are produced by a ballistic calculation program. Which also produces pretty nice graphs suitable for posting.

picture

Wolfhag Supporting Member of TMP26 Oct 2017 9:48 p.m. PST

Andy,
Science stuff guilty as charged!

I bring this techie stuff it up in this forum as I know there are some people who can relate and critique, I have been known to get it wrong. However, it's transparent to the players as I don't want to torture them with graphs, calculations and formulas. Really.

I can't disagree with your recommendations. However, they seem to have been done in numerous games and there is nothing I could improve on. I take a different approach but there is no right or wrong way to do it. I'm kind of a gunnery geek so a game that hits on a 3+ makes me somewhat catatonic. The "technical stuff" is what gives me that "in the turret feel" and I can visualize better what's happening. Is there an easier way to do it and get the same outcome? Probably yes but it won't deliver the same experience for me.

I started with all of the "science stuff" with no regards to playability and then have been cutting it down and making it playable. I think this is a better approach than starting simple and then building chrome and details. Rule #1 is no calculations other than adding a few + or – modifiers based on tactics the player chooses (if any). I have been able to stick to that pretty well by having customized play aids for each gun/tank. Spreadsheet formulas crunched factors down to something easy to understand without the need to calculate and forget modifiers. Rule #2 is no charts. I've been able to eliminate them for the basic version but I'll need some for the detailed version. Rule #3 is when playtesting if players are having a hard time understanding a rule or tactic it needs to be changed or eliminated. The game needs to be intuitive, entertaining and logical without mechanics for mechanics sake or because some other game has it.

I know talking about MPI in 0.1-meter increments sounds pretty petty but it really shows the difference between velocity and accuracy which is a large part of the Error Budget. It's a better way to simulate the different fire control and aiming methods. The basic games uses a traditional D20 to hit # that abstracts the MPI results.

The more detailed version of the game uses the final MPI results compared against the target size ( of target height) decides a hit or miss. So a T-34/76 with a size of 1.2 (2.4 meters high) is hit on any MPI result of 1.2 or less (assuming center mass aim point) so no size modifiers. Hull down targets are 0.4 to 0.5 size, first-time players pick it up pretty quickly. There is a minimum number to roll to get a hit just like any other game.

Wolfhag

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