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Old July 24th, 2007, 12:20 AM
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Default FF&S / FF&S Small Arms issues?

Hello

I've been playing around with the FF&S small arms design sequence, and after crunching the numbers for a shotgun shell got a mass per round over 2 kg. Now admittedly this was a *big* shotgun, but the weight seemed a bit extreme to me, so I did some hunting and tracked down the mass (shipping weight) of some various 12 Ga shotgun rounds, and compared them to the weight of the same 12 Ga shotgun round according to FF&S (and the formula is *exactly* the same in FF&S-2):

Solid shotgun rounds for a 12 Ga:
B&P Big Game Ammunition 12 Gauge 2-3/4" 1-1/8 oz Rifled Slug Box of 10
Box of 10 2-3/4" rounds have a shipping weight of 0.9 lb

Pellet (#8 birdshot) rounds for a 12 Ga
Bismuth ECO Ammunition 12 Gauge 2-3/4" 3/4 oz of #8 Shot Box of 10
Box of 10 2-3/4" rounds have a shipping weight of 0.8 lb

00 Buckshot rounds for a 12 Ga:
Fiocchi Ammunition 12 Gauge 2-3/4" 00 Buckshot 9 Nickel Plated Pellets Box of 10
Box of 10 2-3/4" rounds have a shipping weight of 0.9 lb

According to FF&S, the wieght of a single 12Ga shell should be:
70x3.14159*18.5*18.5*0.003 G = 225g per round. Note that this assumes that the round is 70 mm long, not ~76 mm long
Actual weight is ~40g per round

So this seems to be out by a factor of about 6, fairly significant if this is true across other firearms as well.

Anyone out there have comments on what kind of densities I should be expecting in "real world" ammunition, so that I don't have to go hunting this down for other ammunition types? I'm pretty sure that there are folks out there who can give me the weight and dimensions for .45 APC ammo (for example) so I'll promise to do the calculations for what FF&S says the ammo should weigh, and compare to Real World ammo weights and see if there's a consistent error, or even just a trend across ammunition types. Just so we have a reasonable basis for comparison, FF&S uses the following ammo types:

Shotgun
Straight
Necked

FF&S assumes pistol ammunition is straight, so if it's necked pistol ammo I'll compare both ways to see if "straight" is a good assumption

What I need are the length and diameter of the ammunition, and the weight per round (including the brass / case / whatever)

<EDIT> Of course if you have slug weight, propellant weight and muzzle velocity, I suspect that I'll be doing some work on reverse engineering these as well... </EDIT>

Thanks

Scott Martin

Last edited by Scott Martin; July 24th, 2007 at 12:26 AM..
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Old July 24th, 2007, 01:04 AM
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I had some of this hunted up ages ago. I wonder if the TML Gunlist is still active? I haven't had mail from it for quite a while, it'd be a good place to ask if was still around. Come to think I haven't seen the regular old gun-nuts on these forums for a while either.

The Traveller TNE group on yahoo would be a good place to ask, they are still active and I think the archives have some designs.

http://games.groups.yahoo.com/group/Traveller_TNE/

Oh and VERA and SARA and the BARD pages, if I can track a link to them.

It's been ages since I did any FF&S design and I don't recall any big issues with the ball and powder as long as you didn't stray too far from the mean. Try to make something too powerful or too compact, even if it exists, just didn't work too well. Or maybe I'm just forgetting the problems
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Old July 24th, 2007, 01:08 AM
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hopefully it's limited to the shotguns then: for comparison I used the most common shotgun in current production, and it was *waaaay* off, so it's not like I'm diverging wildly from the mean here, I'm aiming at the middle!

Uncle Bob said that the firearms "weren't bad" but given this, I'm thinking that the firearms aren't bad but maybe the ammo is...


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Old July 24th, 2007, 08:34 AM
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Perhaps shotgun ammo is based on the African Safari model, so the weight of the ammo includes the native guide to carry it for the wealthy hunter.
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Old July 24th, 2007, 11:28 AM
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Quote:
Originally Posted by atpollard View Post
Perhaps shotgun ammo is based on the African Safari model, so the weight of the ammo includes the native guide to carry it for the wealthy hunter.
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Old July 24th, 2007, 11:36 AM
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And the weight of the (sailing) ship to get it to the continent in the first place?

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Old July 24th, 2007, 01:22 PM
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Quote:
Originally Posted by Scott Martin View Post
Hello



According to FF&S, the wieght of a single 12Ga shell should be:
70x3.14159*18.5*18.5*0.003 G = 225g per round. Note that this assumes that the round is 70 mm long, not ~76 mm long
Actual weight is ~40g per round

So this seems to be out by a factor of about 6, fairly significant if this is true across other firearms as well.


Scott Martin
Actually Scott get ready to kick yourself.
The formulae is,
Wa=Awm x Lcc x Pi x r*2

That'd be "Radius" squared not "Diameter" which you have used in your formulae. In that example it should be 9.25 x 9.25, not 18.5 x 18.5.

Though you did say you were talking about a Really BIG shotgun!

A quick rework using your example gives .003 x 70 x 3.14159 x 9.25 x 9.25 =
56grams. Close to real world 40grams, atleast, what is it they say, close enough for government work?
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