M948 SLAP Ballistic information


#1

Hello!

I’m absolutely 100% new to this forum but figured the “International Ammunition Association” would know at least something on the topic at hand. I’m looking for any form of ballistic data possible for the M948 SLAP projectile. Ballistic coefficients, muzzle velocity (preferably as specific as possible), etc.

I’m asking for this information as I’m in the process of creating an addon for a game called Arma 3 and would like to feature this type of ammunition in it and portray it as realistically as possible.

Thank you!
/Garmr


#2

I have a few data points: the M948 fires a 4.02 g tungsten bullet at 1,220 m/s.

The closely related Winchester round for the Swedish Psg 90 sniper rifle fires a 4.81 mm 3.4 g bullet at 1,340 m/s.


#3

Thank you. As of right now I’m mainly looking for info on the Swedish 7.62x51 Sk Ptr 10 PRICK which, in my understanding, is identical to the M948 SLAP ammunition. Do you happen to know the length of the projectile? Or at what temperature the 1,340m/s was?

To give an idea of the data needed:
Projectile Caliber
Projectile Mass
Projectile Length
Muzzle Velocity shifts at -15C > +35C in 5C increments.
Ballistic coefficient in appropriate G model.


#4

As of right now I’m mainly looking for info on the Swedish 7.62x51 Sk Ptr 10 PRICK

That is the Psg 90 round I mentioned above. It does not seem to be identical to the M948. Winchester Olin did a lot of work on 7.62mm SLAP, producing lots of variations in bullet weight, shape etc. As I understand it, one solution was chosen for the M948, a slightly different one for the Psg 90.

P.S. - I have found a little more on the Psg 90 round: the flight time to 1000 metres is 1.4 seconds.

PPS I have found in my file a multi-page document on this round. I will put it together and post it - when I can!


#5

OK, here we go - this is FMV’s publicity document, dated 2003:











#6

Tony, thank you for that.

JGarmr, there is no appropriate G model for this type of small diameter bullet. If you use G7, a form factor i7 of 1.31 will give you about correct velocity at 800 m. But at shorter ranges the computed velocities will be somewhat higher and at longer ranges lower than in reality. The form factor may look surprisingly high, but aerodynamics of very small bullets is problematic.
The 1.31 i7 form factor already takes into consideration that Sweden uses 5 degrees Celsius as standard ammunition and atmospheric temperature. You can therefore use it for ICAO-based computations.


#7

Thank you very much for this information, Tony, it will certainly come in handy.
JPeelen, I’m not quite certain what you mean here, I’m by no means a ballistic expert. I’m a data guy who just happens to be interested in ballistics as of quite recently.
The program I’m using allows for ICAO to be standard atmosphere, however I wonder if there’s some way of translating i7 into G7 or preferably G1 if possible? You also mention that 5C is the standard ammunition & atmosphere temperature used in Sweden, this means that at 5C the bullet has a velocity of 1340m/s?


#8

The equivalent G7 ballistic coefficient would be 0.1789.

The G1 model was developd in the 1880s by French Naval Artillery. They could fire projectiles up to (expressed in modern terms) Mach 3.52. In the Swedish conditions (speed of sound 334.8 m/s), 1340 m/s is Mach 4.0, out of range of the G1 model.
G1 model variations extrapolated to higher velocities exist, but I doubt they are based on real experiments. Ordinary bullets start to deform above 1000 m/s. It is really difficult to do controlled experiments at these speeds.
Experience shows that, if some standard model must be used, G7 (originating in the UK in the 1940s) is much better suited for bullets of slender shapes than G1.
Regarding 5 degrees Celsius: in Tony’s SLAP 2 JPEG file the text says that the presented data applies to this temperature. The graph marked “+58%” shows the velocity curve starting above 1300 m/s.


#9

Alright, thank you again for all this information, it’s truly invaluable.
Unfortunately the way this game system (for Arma 3, part of ACE3 mod) works is that there is a (mostly) identical copy of the ATragMX software implemented into the game, which only accepts a G1 ballistic coefficient. I converted the G7 to a G1 using JBM and I think this should do fine. Right now it’s just a couple more tweaks.

I hope you don’t mind me including yourself and Tony.Williams in the credits for the work once I release it to the public? As previously mentioned, the data and information has been truly invaluable.


#10

Thanks for the kind offer, which I appreciate.
But no, please do not include me in the credits. I have been trying to persuade people to drop using the drag of 19th century artillery shells in 21st century small arms ballistics and would rather not be associated with it.


#11

Understandable, well, thank you for your assistance anyhow, I appreciate it greatly. I think I might start looking into what i7 and alike really is in terms of ballistics because I have never heard of it before.


#12

Also, you don’t need to credit me just for posting public info. Although admittedly it was an amazing achievement for me to be able to find something in my files ;-)


#13

Haha, indeed, thank you for your help anyways, man. It’s greatly appreciated.


#14

I bet both would be happy to receive royalties LOL


#15

Haha, I bet they would, however as what I’m working on is merely a modification to a product of Bohemia Interactive, it’s provided for free to anyone without restriction.