Oh come on,get a grip - weapon dmg silly

[iainjcoleman]

If we assume that the damage done by the projectile is proportional to its kinetic energy, which is a reasonable simplification, then for a given level of damage a faster bullet will have less recoil. This is because recoil is determined by the momentum of the bullet, while damage is determined by kinetic energy.

Ok, if we can safely assume that the gauss rifle's low recoil is due to the small weight of the round, why does it do more damage than a normal rifle? The small bit of reading I've done on guns all point to small, very fast rounds not being that good at doing damage to people. They tend to go right through you and not disrupt a lot of tissue on the way. Usually it's the bigger, slower bullets that do more damage. Example- the 4.6 mm round from the FN P-90 is thought to have very poor stopping power.

My approximation that damage is proportional to kinetic energy was a bit of a handwave, I admit. I'm no expert in ballistics. For it to hold even approximately, most of the energy of the round must be deposited in the target - so small high-velocity rounds that penetrate the target without losing much energy will obviously screw all this up.

My handwavy approach for explaining the high damage of gauss projectiles in Traveller is to assume that the projectiles have been cunningly engineered by science fiction so that they are very good at penetrating body armour, but tend to shatter once they have penetrated a few centimetres of tissue.

 

[iainjcoleman]

I don't think lasers would be good weapons because I think they'd just cause a flash steam explosion on the skin surface ( still hurts ) vs. burning a hole through a body all quick and neat... but I have nothing to back up that idea.

I read something along similar lines a while back, but I'm damned if I can remember where. There's no reason why laser guns shouldn't still be effective, if the energy deposited and the resulting explosion are large enough. It just means that they become really very nasty weapons, rather than the neat cauterising beams of old. Personally, I rather like that idea.

 

[mhensley]

My handwavy approach for explaining the high damage of gauss projectiles in Traveller is to assume that the projectiles have been cunningly engineered by science fiction so that they are very good at penetrating body armour, but tend to shatter once they have penetrated a few centimetres of tissue.

That's a good way of answering that. Some sort of ceramic or plastic bullet that explodes after penetrating an inch or two would do it. Another way of doing gauss weapons might be to lower their damage and just give them a really high rate of fire. Yeah, they might make tiny holes but a bunch of them can cut you in half.

 

[mhensley]

I don't think lasers would be good weapons because I think they'd just cause a flash steam explosion on the skin surface ( still hurts ) vs. burning a hole through a body all quick and neat... but I have nothing to back up that idea.

I read something along similar lines a while back, but I'm damned if I can remember where. There's no reason why laser guns shouldn't still be effective, if the energy deposited and the resulting explosion are large enough. It just means that they become really very nasty weapons, rather than the neat cauterising beams of old. Personally, I rather like that idea.

I thoroughly hated the way that lasers were nerfed in TNE. Of course, I'm not exactly sold on the idea of lasers being used as personal weapons though. Look at the stats that MGT gives them. Laser rifles are as heavy as rocket launchers. This is not a weapon that every soldier is going to carry. It would be a support weapon at that weight.

 

[katadder]

Guess they would be used by people in battle dress

 

[apoc527]

One point here to hopefully clarify the recoil debate. It's been touched on by multiple posters here, but not fully explored. There is no question (NO QUESTION now, to whoever was arguing about conservation of momentum) that when you launch a projectile out of a railgun, the weapon recoils, that is, the momentum imparted to the bullet is also imparted to the weapon.

What we should be talking about here is what gun enthusiasts call "felt recoil." It is, often, what people mean when they say "that gun doesn't recoil much." Felt recoil is a function of actual physical recoil (the momentum thing), the weight of the weapon, and the ergonomics of the weapon, as well as any special recoil reducing technology, such as springs or rods in the buttstock.

Thus, it is quite possible that a gauss rifle has very little felt recoil, but that is not to say that it is "recoilless." Modern comparisons bear this line of reasoning out--a .38 caliber bullet fired out of a full sized K-frame S&W revolver is going to have noticeably less "recoil" than if you fire that same .38 round out of a J-frame scandium or titanium "airweight" revolver (this is not fun, and don't ever try shooting full power .357 magnum rounds through one if you are simply trying to enjoy yourself). Thus, a 4 kg gauss rifle firing a small 3mm dart is going to feel like it recoils probably about as much as a .22 LR fired out of a full-sized rifle--that is it say, you could put the stock against your nose and fire and not get hurt.

 

[mhensley]

that is it say, you could put the stock against your nose and fire and not get hurt.

kids, don't try this at home :lol:

 

[Ishmael]

an alternative to "no recoil" is to go the route of recoiless rifles.
The recoil's momentum is imparted to the gasses or to a mass that is ejected from the gun.
no recoil for the gun, but conservation of momentum is maintained.

I don't think TNE nerfed lasers. CT did and it resulted in 'gravitic lensing' within the mount.
Feh! non of that namby-pamby grav tech for me!
If lasers are much shorter range because of that...too bad...get closer.... KK ball-bearing warheads and Mirvs and other less 'laser-y' stuff is good enough for me.

 

[GypsyComet]

Recoil has "flavors", in addition to simple action-reaction kinetics.

The basic relationship is the simple mass and imparted velocity equation.

Then there is the question of center of mass, the moment arm of the applied force and the moment arm of the grip the user has on the weapon(which is why recoil tends to lift the barrel).

Next you look at the nature of propulsion, since the options for recoil suppression are defined by it. This is where the Gauss weapons get their biggest difference, as they are not using an explosive hot gas hose effect to fling the round down range. Firearms that use some relative of gunpowder are using a mostly contained explosion that can only expand in one direction: down the barrel. It's why they "kick", and why a wide variety of gas venting tricks work to mitigate the recoil to a greater or lesser extent.

Gauss weapons are using magnetics to fling a (typically) smaller and faster round, and can use barrel venting that would render a gunpowder weapon useless. Right away this means a couple of things: no explosion to create kick, no hot gas hose following the round, and considerably less air involved in the trip down the barrel. The pattern of force delivered by the purely momentum-based recoil can in fact be a design specification, but will likely default to a fairly smooth waveform (while gunpowder delivers a high spike that slopes back to zero). Smaller rounds with no explosion-containment requirements also allows the action to be designed differently, with even more opportunities to reduce "felt" recoil.

 

[klingsor]

The problem is that a firearm still has to accelerate the projectile very, very quickly to be any use so a gauss gun will still behave much like a conventional firearm. A longer, slower acceleration is simply not a luxury not available to hand held firearms [1]. The ability to achieve a high enough acceleration combined with high density energy storage are the two tricks that will make hand held gauss guns feasible – and the former might have already been achieved.

You do not have the gases, so that will reduce real recoil fractionally and perceived recoil significantly while you will loose the option of muzzle breaks and the like as they work with the gases. In general though you are making much more efficient use of the energy you are using.

A 5,56mm S109 bullet has a muzzle velocity of 930 m/s so it has to accelerate to this velocity in a barrel that is 508mm long from zero starting velocity. That means an acceleration of thousands of Gs – my rough and ready maths suggests something like 87 thousand G which seems excessive even to me [2]. The recoil is going to be 3.67 N not including the gas as I cannot find a figure for the loaded cartridge mass to calculate the mass of the gas (= loaded cartridge mass - bullet mass - case mass (near enough anyway)).

Notes
1. I know this is an important factor affecting things like powder choice and grain shape but not at the sort of scale that could be perceived by a user. The effect on artillery would be much more interesting.

2. O level maths rides again.
V^2 = U^2 + 2as
Where
V = 930 m/s
U = 0 m/s
s = 0.508 m

930^2 = 2 * 0.508 * a
a = 930^2 / (2 * .508)
a = 851279.5 m/s^2

Seems too high but I cannot see an error. Help!

 

[zozotroll]

I cant help with the math, but I remeber from somewhere that an arty round pulled in the order of 1900 G's. Of course, that is over a 19' barrel, so rifles will be much shorter.

As for mass of the gas, I recall from a couple decades ago that a 5.56mm round used around 20 grains of powder. Memory could be off a little, but the case is to small to hold much more. If you need a more precise number than that, let me know, and I will dig out a reloading manuel and give you a range.

 

[GypsyComet]

The problem is that a firearm still has to accelerate the projectile very, very quickly to be any use so a gauss gun will still behave much like a conventional firearm. A longer, slower acceleration is simply not a luxury not available to hand held firearms

I was thinking more along the lines of an even acceleration all the way to the end of the barrel, instead of the lop-sided spike you get with gunpowder. Same area under the graphed curve (so the same force applied overall) but the curve itself is shaped very differently.

Late edit: This is more an issue for "felt recoil" (per the post by apoc527) than actual.

 

[klingsor]

I am pretty sure I have figures here somewhere in The Database from Hell - if nothing else Barnes will probably have something close enough though really this is all a little bit pointless, the RPG equivalent of arguing over how many angels can dance on the head of a pin.

The one time I successfully got any of the recognised bullet effectiveness formulae to agree with any RPG was for Deadlands with Wootter's Lethality Factor. The problem there is that I think that formula has well known problems and is basically junk – which makes it a good match for Deadlands as I have real problems with that system. I cannot even find where I first saw the formula either though I am pretty sure it was a in an issue of the American shooting magazine Guns & Ammo.

If I were starting from scratch I might take one of the better formulae, Hogg's is one I am quite partial to and use it. The problem is the subject is so poorly understood that even the so called experts bicker constantly and any formulae is at best a poor attempt to model a very, very complicated subject as every shooting is unique.

Trying to model firearm damage leads to excess complexity for the system. GURPS for example worries about what type of bullet you are using (or used to anyway in the superb if misnamed High Tech). Now I am tending towards simplicity, the system is just a vehicle. At this rate I will end up using a story telling system.

I rather suspect that a small die roll multiplied by the amount by which you made your roll might be the best way to do it so allowing for both skill and outrageous luck to play their part.