Low-Tech Missile Weapon Range and Accuracy

[Icelander]

Originally Posted by DouglasCole

Interesting. I hadn't thought to vary draw weight multiplier with skill. Increasing ST is the functional equivalent at constant multiplier, however, although I suspect your numbers above have more granularity than just (say) +1ST at DX and +2ST at DX+2 or something.

All guides on the subject say that a new archer will find that he can draw a bow of about 10 more pounds once he's had a few days or weeks of practice. That suggests to me that even a single point in Bow ought to be worth something.

I also believe that a reasonably strong archer will have exercised different muscle groups than a very strong weight lifter. It seems fair to me that the archer could pull a bow more efficiently than the weightlifter.

Given that most hobby archers will be at DX+1 or lower (except the exceptionally dedicated ones), this also means that a normal man (ST 10-11) will use a bow of about #45-#75, with the higher numbers being reserved for thsoe who are fit and practise a lot.

Originally Posted by DouglasCole

If we "believe" (or really, we wish to stipulate) the equivalent of +4 to ST through skill - or if we say that you can pull, say +40% heavier bow with special exercises and +40% with technique, rather than +2ST for each, then you could easily, say, give +10% to allowable draw weight at DX, with a +10% more per point of skill higher, capping at +40% at DX+4 or DX+5 in realistic campaigns. Likewise, charge 4pts per +10% for "special exercises" or something. Easier would be allowable up to +2 arm ST with the special Exercises perk and +1 at DX and +1 more at DX+2 or something.

Net/net, though, once you've spent the points in archery, presumably that's worth something as you say.

People who practise sports that value upper body strength tend to develop a corresponding musculature. I find the Special Exercises (Arm ST) Perk reasonable and realistic. It's mostly whole body ST of 15+ that I find unrealistic, and that only because of the striking ST component.

Originally Posted by DouglasCole

It wasn't an "experiment." I took my stats from the very useful article "The Physics of Medieval Archery" [http://www.stortford-archers.org.uk/medieval.htm] which give physics-based estimates for the strength of bows of the period, as well as estimating the velocity and mass of the projectiles themselves.

From this, using bullet impact formulae I derived in my article on GURPS bullet damage in Pyramid, I can calculate the points of armor a projectile of certain cross section and energy would penetrate. For a "muzzle velocity" of 60m/s and a weight of 60g, and a 1cm diameter shaft, you get about 3.8pts (1d) calculated penetration. This is complicated by the arrowhead, which has a MUCH lower cross section than the shaft, but even a cross-sectional area more accurately calculated (say, a trapezoid 4mm at its thickest and 30mm wide as a broadhead point) won't be less than about half that of the shaft, which only changes damage by 10% higher. (3.8pts goes to 4.2pts). What MIGHT drive that number higher is if the arrowheads were hardened or forged or something much harder than the jacketed lead or mild steel my model was built around. That would usually add an armor divisor...with good steel (semi-armor piercing) usually being worth a 1.25 to 1.5 armor divisor. That would typically make an arrow from this bow penetrate like 1d+1 (4.5pts) to 2d-1 (6.3pts). Given how much oomph I think we can all agree is required for a draw of 180-200lbs, having THAT bow eke out no more than 2d damage as a "ST20 bow" upper end would be fairly OK. That's thr or thr+1 using the ST table AS IS. But, it also requires the assumption of hard arrowheads and smaller cross section...which frankly ain't that bad.

Crossbows, apparently, have the benefit of not requiring so many points to eke out that same damage.

So the best we can do is thr+1.

Question, what difference would composite bows make here? Enough for a +1 damage over a yew longbow? Another question, what if we postulate fantasy materials that are lighter, springier and better? Do we eke out more damage or are the limitations not related to the material used?

Originally Posted by DouglasCole

My impression, mainly from this forum, is that arrows would rarely punch through metal armor.

This is also my impression. But, then again, the same applies to single-handed swords. So at least a part of the problem is ST damage.

If we are not going to monkey about with that, we'd probably want to benchmark bow damage at ST 10 level and accept that high ST will give unrealistic results. Otherwise bows are artificially weaker than melee weapons, which monkeys with relative weapon power.

[Icelander]

Originally Posted by nik1979

I feel those stats are correct and accurate. In a game perspective a hero with a xbow will kick ass but, rarely are these weapons used by heroes.

The problem that I have is that the GURPS stats are... somewhat optimistic.

For example, according to the rules as written, it takes 4 seconds to load a crossbow. This is true, for the lighest hunting crossbows. But such crossbows can't reach the range or the damage given for the GURPS crossbow. A more realistic assessment for a war crossbow would be 8 seconds or more.

And the Crossbow in Basic is evidently supposed to be a TL2 selfbow. Everyone who is anyone at TL3 will be using the more efficient and powerful Composite Crossbow. Let's look a professional crossbowman. Crossbow at DX+2, Crossbow Finesse Perk and ST 11 wouldn't be out of place, would it?

He can fire his crossbow at a rate of 10-12 times a minute (equivalent to historical bows and more than twice as fast as the most optimistic estimates for historical war crossbows). He inflicts 1d+5 imp damage, which reliably penetrates plate armour and puts most lightly armoured foes down. His 1/2D range is 325 yards, which means that he can penetrate plate at over 300 yards. His maximum effective range is 450 yards.

But most jarring of all, his Acc is 4. That's right, any crossbow, whether TL2, TL3 or TL4 has a better Acc than a Baker Rifle. Even without effective sights, mind you.

Do we really believe that at a 300 yards range, it's equally difficult to hit a target with an M4 carbine and a historical crossbow? And that if the bullet hits, it's going to do an average of 16 points of damage against an unarmoured person vs. the crossbow's 17?

Originally Posted by nik1979

I've read up and discussed with some friends the studies about the bow, the xbow and the muskets (even the handgonnes). A friend (who lurks these forums) as told me about some calculations made to see how these two technologies would interact.

From his anecdote a program running a simulation of 13C longbowmen of 5,000 against an equal no. of Napoleonic Riflemen. Depending on the circumstance they can defeat each other quite soundly. Bottomline is basically the morale, the first to receive a terrible loss would be the loser.

Very true, but not quite relevant. We know that the longbow was a tremendously effective military weapon when used by men who had grown up with them. Rifles and muskets, however, didn't require more than a few weeks of familitarisation. Huge difference. France could conscript millions of men with muskets, but there weren't ever millions of longbowmen.

The problem with the GURPS stats is that even a ST 11 soldier given a few lessons on how to use a Bow (1 point for a DX-1 level or a skill level of 9) will usually be more effective with a Composite Bow than any kind of musket or rifle before the 19th century. And the same applies with crossbows.

Originally Posted by nik1979

Stat-wise, I find them correct. It is the context of what happens when the typically bad circumstances in war that alter what is theoretically probably from what will happen.

Granted, war is different from small-unit skirmishes, but that doesn't chance the fact that GURPS overstates Accuracy for low-tech weapons.

Originally Posted by nik1979

Food for thought. My friend who is reading up on many Chinese texts about their combined arms tactics found that they employed the Rotating Massed Volley Fire with their Heavy Xbows (contrast to the squad firing as quickly as they can, continuously), similar to those employed with early slow loading rifles. Between volleys, they would have archers step up and, with rapid fire, fill in these crucial gaps. An amazing sight IMO, if xbows use matured fully and combined with archery.

Yoink, stolen for some fantasy culture, haven't decided which one. I've already stolen jannissary tactics for my rising hobgoblin culture, so I'm not sure where to fit this...

;)

[Icelander]

Originally Posted by fredtheobviouspseudonym

GURPS should not give a heavy crossbow 25 shots per minute. A light crossbow (no more draw weight than a small bow) perhaps -- but there wouldn't be much aiming.

I quite agree. But this is without aiming, with the Fast-Draw skill and no accuracy at all.

With aiming, a skilled crossbowman goes down to the 10-12 shots per minute mentioned above. Still too high, in my opinion.

Originally Posted by fredtheobviouspseudonym

As a number of sources, including the Royal Ordnance Museum (IIRC -- it was British gov't facility) have noted, longbows will not penetrate decently-made plate armor from c. 1450 on. Said outfit made repops of both bow & armor, (actually, armour, being British) fired A at B at a range of less than 10 meters, and arrows bounced without so much as denting the surface. I've seen the film; plate existed for a reason.

Heavy crossbows could -- but they were problematic. If you're holding a 1500 pound draw weight any flaw in the metal can & will be fatal. At least one monarch, a king of Scotland, died in a hunting accident when his crossbow went SPROING! and inflicted heavy injury.

Do you know of any research that indicates the approximate penetrating power of crossbows of various draw weights? That would be an invaluable source for benchmarking realistic crossbow stats.

Originally Posted by fredtheobviouspseudonym

In some ways a heavy (c. 1500# draw) crossbow is a more difficult manufacturing task than a musket. While the latter has to survive more peak pressure, no part of it has to be terribly hard AND have great tensile strength. The tips of the crossbow and the faces of the trigger mechanism thereof do require this. If the tips are soft, the bow-wire will cut into them and (if you're lucky) disable the crossbow. If you're not lucky the tip will separate. Given the geometry of the crossbow, if you're aiming it at the time a wire lash will hit you driven by c. 750# (a single bow-limb). Not good.

A #1500 draw crossbow should be much more expensive to make than a musket. It should be about as expensive as a good sword.

That aspect, at least, is accurate enough in GURPS. As long as you assume that most medieval crossbows were steel or composite and cost $950 or more. The Basic Set crossbow is obviously a self-bow.

Originally Posted by fredtheobviouspseudonym

And, as stated, it was easier to train a man to use a musket than a longbow.

Very true.

Originally Posted by fredtheobviouspseudonym

As far as accuracy, the Knights of St. John at Malta (1565 CE) noted that Turkish musketeers were inflicting hits on single targets (human) at over 100 yards in the siege of Fort St. Elmo. While they may no have been accurate by our standards they were accurate enough to be a problem.

As previously stated, I feel that muskets are realistic enough in GURPS. It's just that crossbows and bows weren't reduced in Acc with the edition change. Meaning that bows and crossbows are much more accurate in combat than they should be.

[chris1982]

Well I think denying an enemy the use of a shield is enough justification to use gunpowder weapons instead of crossbows.

[Icelander]

Originally Posted by chris1982

Well I think denying an enemy the use of a shield is enough justification to use gunpowder weapons instead of crossbows.

The shield still grants its DB and Dodges are allowed by RAW. Denying the use of the shield is a benefit, true, but at the cost of 2 points of Acc? That's ftwo times the effective range.

[vicky_molokh]

Originally Posted by Icelander

The shield still grants its DB and Dodges are allowed by RAW. Denying the use of the shield is a benefit, true, but at the cost of 2 points of Acc? That's four times the effective range.

Huh? A +2 to Acc is ×2 to range. Where's four times?

[Icelander]

Originally Posted by Molokh

Huh? A +2 to Acc is ×2 to range. Where's four times?

Sorry, extra doubling there. ;)

That's more than two times, yes.

[Icelander]

Douglas, regarding the velocity number of 60 m/s, I've found sources (including The Knight and the Blast Furnace) that indicate that 50+ m/s is easily achievable with yew longbows of #75-#80 draw weight. I admit that this is using a 50g war arrow, but a 90g broadhead only slow it down by about 20%. Initial energy would be around 70J-90J.

Shouldn't a #150 yew longbow get more speed?

The same experimenters (McEwen et al) got a speed of 62 m/s with a #90 draw weight crossbow firing a modern target bolt. Energy with a 100g bolt would be 192J.

Can you spin these into GURPS damages?

[Icelander]

I was thinking that loading at the speed given in Basic Set would allow a crossbow with a draw strength of 2xBL. Using a stirrup allows up to 4xBL. I suppose that a two-footed stirrup could allow up to 6xBL, but would take more time than a belt-hook and be less comfortable.

Heavier draw weights require mechanical aids, such as the belt hook and stirrup. Those would allow 6xBL. A two-footed stirrup and a hook would possibly allow 8xBL and a goat's foot lever would probably reach the same.

That means that a ST 11 professional soldier can draw a war crossbow of #192, if he has the Crossbow Finesse Perk he reaches #272 and the strongest soldiers (ST 16 + Crossbow Finesse) were probably around #520.

I think that crossbows of #150 draw weight were historically used by Genoese mercenaries, but that might have something to do with them wanting to be able to draw them by hand. I'm having trouble finding good sources on Genoese crossbows. Testing was done on a #1200 model, but that's hardly a battlefield weapon.

A cranequin should probably be rated independently of the users ST, but perhaps the speed which the user can load is dependent on some combination of ST and skill.

The windlass isn't really ST-dependent.

[jacobmuller]

Originally Posted by Icelander

Ability increases don't use the 1 CP = 200 hours mechanism.

Rasing ST doesn't take anywhere near 6-12 years. Just look at a lot of athletes throughout history who've gone up weight classes or improved their performance.

Okay.
You still need to find ST+1 recruits for bow use. Muskets and Crossbows don't require exceptionally strong recruits. They take half the time to train to a given standard. I'd take the RAW Bow stats as correct. About the only change I'd make is finding a way to handle the difference between arrow heads; target, broad, bowel-raker, blunt, etc. Muskets are powerful enough and they weren't renowned for accuracy. We do, however, have tales of accurate archery/ crossbow shooting. Time was, I could put an arrow in the cup at 50 yards with a borrowed practice bow and used target arrow while using a pin and cellotape for sights. Muskets were deemed remarkably accurate if they could hit a man-sized target at 100 yards.
Perhaps you're over-rating powder and under-rating muscles?