Muzzle velocity

[Scipio]

Why has each gun in CM the same muzzle velocity for all ammos? It must be different for each type of ammo, too. For example the German 3,7mm AT gun:

110 m/s Stielgranate ©

675 m/s Sprengranatpatrone (h)

745 m/s Panzersprenggrante (Panzergranatpatrone) (a)

1020 m/s Panzergranatpatrone 40 (t)

[Doug Beman]

That sounds like a good question, and the only answer I can come up with is "perhaps the muzzle velocity of any shell, right at the opening of the muzzle, is the same. The difference comes with range, where different shells will lose velocity at different rates."

DjB

[Scipio]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Doug Beman:

perhaps the muzzle velocity of any shell, right at the opening of the muzzle...<HR></BLOCKQUOTE>

This is the one and only muzzel velocity = Vo, and must be different for all ammo types.

[Jeff Duquette]

Muzzle velocity is not constant within the same weapon firing different types of ordnance. Muzzle velocity isn't even constant between rounds of same ammunition. Initial Powder temperature, manufacturing lot of ammunition, and barrel ware can all result in subtle contrasts in muzzle velocity. Initial powder temperature can result in as much as a 5% contrast in muzzle velocity between say 70 degree F and 0 degree F.

Muzzle velocity will change (within the same weapon) dependent upon, interior ballistics of the barrel and projectile, as well as --among other things -- the charge employed. Example: US Howitzer 105-mm M2A1 firing M1HE Shell:

Charge 3 muzzle velocity vo = 780 f/s

Charge 4 muzzle velocity vo = 875 f/s

Charge 5 muzzle velocity vo = 1020 f/s

Charge 6 muzzle velocity vo = 1235 f/s

[ 10-13-2001: Message edited by: Jeff Duquette ]

[Scipio]

Ooohps - forget it

[ 10-13-2001: Message edited by: Scipio ]

[Redwolf]

Just did a short test. In CMBO, the Panther's HE shell is slower than the AP shell.

[Mud]

So, probably, they only list the AP muzzle velocity, the same way the single listed blast rating is very likely just for the HE shells.

How often is penetration an issue when you're firing HE? Perhaps against a soft-skinned vehicle, but... There's accuracy as well to consider, but again, firing into a mass of infantry in woods with HE probably does not need quite the same degree of precision as does trying to bounce an underpowered round off the shot trap of an early Panther turret and then through the top armor. So, eh, it seems plausible to me.

[Pascal DI FOLCO]

AFAIK, speed is not really an issue for HE nor HEAT : it affects "time on target" and thus (indirectly) accuracy on moving targets, but any effect (be it on vehicles or soldiers) is explosive/chemical, not kinetic.

However I wonder about Tungsten : these were really high velocity kinetic ammo, so the game engine *should* track correctly their speed... I saw no reference to that ever, so if someone has info :confused:

[Jeff Duquette]

I think the question was “Why has each gun in CM the same muzzle velocity for all ammos”. With a few notable exceptions, the answer is: In reality muzzle velocity is not typically the same between different ammunition types fired by the same gun. I’m not sure how HE and armor penetration has anything to do with the question. If the question is; “Do the muzzle velocities indicated on the CM unit reference screen effect armor penetration”…I doubt it. I am guessing that penetration for a specific AP ammunition type is laid out in penetration data tables which were no doubt calculated based upon actual projectile impact velocity relative to range and angle of obliquity\ angle of attack. Presumably BTS employed the Milne de Marre equation for armor penetration at angles and impact velocities that are not normally laid out in common references.

AFAIK rotational velocity does effect HEAT and it ability to penetrate. Barrel rifling and resultant projectile spin was an extreme determent to shaped charge penetration during WWII. High rotational velocity affected the plasma stream focus.

[Vanir Ausf B]

From page 59 of the CM manual:

<BLOCKQUOTE>quote:</font><HR>Internally, Combat Mission tracks the weight, velocity, and size of explosive charge of all the different shell types from all the different guns in the game individually.<HR></BLOCKQUOTE>

[Crash-Neptune]

This reminds me of another question. What does the L mean as in 8.8cm L/56 or 7.5cm L/70. I'm guessing its length of gun barrel in calbers, I've heard that before, but I'm not sure. Also, how long is a caliber?

[Vanir Ausf B]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Crash-Neptune:

This reminds me of another question. What does the L mean as in 8.8cm L/56 or 7.5cm L/70. I'm guessing its length of gun barrel in calbers, I've heard that before, but I'm not sure. Also, how long is a caliber?<HR></BLOCKQUOTE>

You're on the right track. To find the length of the barrel, multiply the L number by the bore size. So the 88L56 is 8.8cm x 56 = 4.93m long. For German tanks this would include the breech, but not any muzzle brake.

[ 10-13-2001: Message edited by: Vanir Ausf B ]

[Cpl Carrot]

Yep L stands for length of gun in calibres. The calibre is the first number. So an 88/56 is 88cm*56cm or 4928cm long (4.928m). The 75L70 is therefore 5250cm long (5.25 m). Hope this helps and I have it right

Damn my slow fingers

[ 10-13-2001: Message edited by: Cpl Carrot ]

[Crash-Neptune]

so 88cm time 710mm is 62480 mm which is 6.248 m?

[Gen-x87H]

My only guess is they are taking the AP velocity as this is the most common type of Ammo used against armor.

But internally I suspect if Tungsten rounds did have a higher velocity it shows up in the penetration charts.

but it would be nice to see the velocity of all types of ammo

Gen

[Pascal DI FOLCO]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Crash-Neptune:

so 88cm time 710mm is 62480 mm which is 6.248 m? <HR></BLOCKQUOTE>

Right ... That means I can't put a 88L71 in my bedroom

[Rodimzew]

BTW...some other data may be of interest...

8,8cm-Kw.K.43L/71

available ammo :

Pzgr.39-1, 10,2kg, Vo 1000m/s

Pzgr.40/43, 7,3kg, Vo 1130m/s

Penetration on 30° sloped armor:

Pzgr.39-1 202mm(100m), 185mm(500m), 165mm(1000m), 132mm(2000m)

Pzgr.40/43 237mm(100m), 217mm(500m), 193mm(1000m), 152mm(2000m)

Within the CMBO timeframe, the Pzgr.40/43 was very rare. And even if it were available, due to the thin allied armor you would not notice it. I assume it was designed to penetrate monsters like a Stalin2.

AFAIK some tables like that above are used in CMBO. IMO even the graphic display is considering Vo's. There is a significant difference in time delay (fire to impact) between i.e a firefly and a sexton...