Here is what you (realism) players always wanted to know about (old)
range-weapons, and esp. the
sling in the bottom third part of the essay:
'The sling in medieval europe'
http://www.chrisharrison.net/index.php/Research/Sling
A short info: A sling applied by a real skilled "professional"
slinger was superior to an archer ... valid and evident for the warfare in antique times (fe. google for Balearic Slingers, Rhodian Slingers), in some locations also later.
The thing is, the art to apply the sling effectively (deadly in battles) disappeared during medieval times due to a change of the socialisation of the people.
In our Brytenwalda world realism-wise, there would be hardly any "professional" aka real deadly slinger, while
shepards would have been probably the ones, which applied that at best.
Further on, bowmen:
Afaik, the so-called "Welsh Archer" was unknown at the time, while the celtic Britons and Welsh were probably better archers than all other on the isles. Why? I believe nobody knows the reason, because effective bows themselves, esp. the longbow wasn't an invention by the celtic Welsh (or Britons), it was fe. even so known and applied by northern continental people, but just not so much as warfare, to say the least. A thought might be, that in Roman times, the celtic native hunters of the many forests were engaged as range auxilia units (personal assumption), and as hunters for the legions. Another reason might be, that the Britons and esp. also the Welsh were very poor people, and a warrior garment wasn't affordable, so bows, but mainly javelins and tool-axes (plus knifes and clubs), were the primary weapons of the common people aka peasants, and hunters (the better bowmen, but still only few). The germanic invaders (Saxons, Engles, Jutes and Frisians) were superior in melee warfare to them, due to a melee warrior tradition in their tribes, which probably merely saw a bowmen (and skirmisher) as coward.
