Ballistics spreadsheet discussion

[DouglasCole]

Ballistics Spreadsheet Google Docs

SimonAce's Blog

Hosted on mediafire

Three links for my spreadsheet. Wanted to move this here to keep from derailing the controllability thread on .40 S&W overmuch.

Edit:

I'm posting this up front because it's come up a few times. The published in-sheet data for the 7.62x25mm Tokarev is very wrong. Use these values insted:


INPUT
7.62x25 Tokarev
Chamber Pressure 35000
Barrel bore 7.62
Case Length 25
Chamber Bore 7.62
Barrel length 120
Bullet Mass 86
Aspect Ratio 1.5
Burn length 10.5
Projectile Caliber 7.62
Total Accelerated Mass 86
Expansion Ratio 1.5
Projectile Load 1

This isn't the hottest load out there by a long shot, but it's representative of an "average" cartridge. My understanding is that the hottest load is 35-40,000 psi and develops 760J from a 120mm barrel with an 85 grain bullet.

The values posted above will give the damage listed in High Tech (3d) when fired from the 260mm barrel of the PPSh-41, about 11.3 points of damage.

[DouglasCole]

"Also the action type section seems broken, at least for me. When selected spits out numbers rather then the type and causes weights even for say pistol cartridges in the thousands of pounds. "

This is probably true. I might have an old version where the weapon design stuff works, but that sheet has hacked it beyond recognition.

It was basically a formula that took the pressure, figured out what thickness of steel would support it properly, added in a factor for materials strength, and calculated the barrel weight by that cylinder thickness multiplied by barrel length. Added to that some factor for action type, plus extra weight for a stock or not.

[Jonas]

Originally Posted by DouglasCole

"Also the action type section seems broken, at least for me. When selected spits out numbers rather then the type and causes weights even for say pistol cartridges in the thousands of pounds. "

This is probably true. I might have an old version where the weapon design stuff works, but that sheet has hacked it beyond recognition.

It was basically a formula that took the pressure, figured out what thickness of steel would support it properly, added in a factor for materials strength, and calculated the barrel weight by that cylinder thickness multiplied by barrel length. Added to that some factor for action type, plus extra weight for a stock or not.

Aah, I didn't realize that function was more vestigial then anything. I had to ask however as for all I knew it could have been Open Office on my end not playing nice with the spreadsheet.

[Sam Cade]

Nominal velocity is off for the 7.62Tok. Its listed at 307 m/s should be higher..MUCH higher. I was getting north of 1500 fps with the last bunch of purple flame spewing surplus I shot.

[AmesJainchill]

Originally Posted by Sam Cade

...last bunch of purple flame spewing surplus I shot.

Seriously?!? Purple?!

...Awesome!

[lexington]

Originally Posted by Sam Cade

Nominal velocity is off for the 7.62Tok. Its listed at 307 m/s should be higher..MUCH higher. I was getting north of 1500 fps with the last bunch of purple flame spewing surplus I shot.

Depends on the exact type. I guess different makers have different powder mixes?

As low as 1076fps.
http://www.makarov.com/tokloaddata.html

As high as 1641 fps.
http://www.wolfammo.com/index.php?op...id=2&Itemid=13

[Sam Cade]

Originally Posted by AmesJainchill

Seriously?!? Purple?!

As purple as Prince's panties.

The smell when fired is strange too, oddly fruity... anything is better than the infamous hungarian cat-**** smell.


1955 Headstamp.
Polish.
http://img69.imageshack.us/i/headstamp.jpg/


Dig that crazy crimp. 3 equidistant indentions.
http://img560.imageshack.us/i/crimp.jpg/

[DouglasCole]

Originally Posted by Sam Cade

Nominal velocity is off for the 7.62Tok. Its listed at 307 m/s should be higher..MUCH higher. I was getting north of 1500 fps with the last bunch of purple flame spewing surplus I shot.

I wonder if I wound up statting up the subsonic Chinese variant used in suppressed weapons. Would make some sense, since about the same time I was doing my spreadsheet I was also doing my Black Ops campaign, which had a big China connection.

[Ogo]

First, I want to say that this is such a cool resource. It’s pretty amazing to be able to look up real-world guns on the web, and once you know the round characteristics and the barrel length, get game-able stats for them! Amazing stuff.

But I do have a couple questions, since these equations will spit out numbers that are slightly different from High-Tech. I’ll address these to Douglas but if anyone else with more mathematical insight than me (read: just about anyone!) wants to chime in, thanks much.

1. Converting points to dice of damage:

The formula used to convert points to dice...

(I’ll reproduce it here in its spreadsheet format: =CONCATENATE(INT(A15/3.5),"d+",FLOOR(3.5*(A15/3.5-INT(A15/3.5)),1)) )

This’ll give you you +1, +2, or +3, which is a little bit different w/r/t the decimal fraction +adds from the conversion outlined in HT, for +P rounds and the like:

(I hope this is ok to reproduce here)

0.0 to 0.14 +0
0.15 to 0.42 +1
0.43 to 0.64 +2
0.65 to 0.85 +1d-1 [+2.5, if you like]
0.86 and up +1d [+3.5]

You can see that these different approaches will nudge damage in different directions “within” a given dice of damage. HT can bump things up to another +1d, but the FLOOR calc above can’t. What are the implications for this? Can anyone speak to the thinking behind the HT version? There’s some statistical mojo here that I don’t understand, probably.

2. The equations themselves:

The basic damage equation you built: Damage (points) = sqrt(KE1.04/Xsect0.314)/13.3926, produces number that are slightly different from HT canon (which is the whole point, obviously!).

But can anyone show us “under the hood” at how HT’s numbers were derived? I’d like to be able to make some comparisons, if possible!

Some differences leap out at me right away: Douglas’ sheet gives us a standard 9mm pistol with 9.3 avg. dmg, a little better than the canonical 9. If you used HT’s method of converting that back to dice, you’d get 3d-1.

So in short, I’m looking for a little more info on what went into HT and how that compares to Douglas’ work here. I know there are a billion HT threads and guns are a contentious subject etc, etc, I hope I’m not kicking too many hornets’ nests here!

[SuedodeuS]

I think HT's stat lines were based on actual real-world penetration of RHA steel (or equivalent), whereas DouglasCole's spreadsheet is essentially calculating said penetration.