Low-Tech Missile Weapon Range and Accuracy

[DouglasCole]

Originally Posted by Icelander

Since this is for personal use only, I don't mind complicating things a bit. In my view 2xBL is reasonable for someone unskilled, 2.25xBL for anyone with any training at all, 2.5xBL at DX-level, 2.75xBL at DX+1 and finally reaching 3xBL at DX+2.

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.

Strongbow Perk is only for those who have 10 points or more in an archery style, which I'd say is rare for a modern man, but reasonable for a historical archer. It works normally in this scheme.

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.

Do you have data about the experiment?

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.

Do we think that longbows can punch through armour?

I think that the occasional high damage roll representing a lucky angle or hitting a weak point is fun and gamable, but I don't think that arrows historically penetrated armour at all.

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