Maybe I'm not understanding something about the physical makeup of your races, but a recurve bow is a weapon of war, especially useful in "brush and forest terrain, or while on horseback," that is more efficient at storing and deliving energy than a regular bow.

Are you seeking more than the obvious answer of telling them to "aim for the eyes"?

@Frostfyre It's useful for both hunting and before guns war. Hunting bows are smaller draw weight because you usually stalking the prey, bestrecurvebowguide.com/… english warbows go more then 100 lbs longbow-archers.com/heavybows.html

Leather Armour was never really popular. Gambeson on the other hand: youtube.com/watch?v=-uWDCDJD_4w Also, your table literally added nothing of value as you forgot to mention what draw weight would your gnome warriors be able to handle, and you're asking archery experts who'll already know basics like this, as they went through those phases. While interesting to non-experts, without comparison, it does nothing.

why not use javelin for this gnome cavalry ? or crossbow instead, or you can also use sling. are this weak hunting bow a must thing ?

besides if they are a mounted cavalry already, why not just turn them into charger or lancer instead,especially as light cavalry, seems more plausible rather than forcing them to use weak draw bow as horse archer substitute.

@FailusMaximus Removed table, added expected draw weight of gnomes as half of what humans could use. Roughly gnome warbow is equal to human hunting bow.

@LiJun Crossbows exist in my world but good ones are expensive, plus nobility doesn't like their mass production in order to avoid to fall in the hands of the peasants. Why would the Javelin be any better? I've never heard of horseman using slings.

@LiJun I think it's better to ask different question, how best could they be used. From my story they are there, they are cheap, and commander lacks troops. I need to figure out how best to use them.

@FailusMaximus They ride small ponies, something like Shetland ponies, which could be acquired for relatively little, and can't be ridden by adults horseforum.com/horse-riding-horse-activity/…

Technique has more to do with it then strength. I'll always remember the old man that could barely walk, shuffle up to me and show me how to pull back a bow that was 100 pounds of weight on it. He did it effortlessly, I struggled at 70.

Crossbows really will make more sense, especially if your gnomes are gifted with some Jörg Sprave ingenuity.

In reality, accuracy pretty much only matters for snipers. You just aren't going to have anything with sniper range and precision without guns. Only in video games and zombie invasions do you aim for the head; in real life you want to aim for the chest since it's the biggest target. A bullet or arrow will most likely kill you whether it hits your head or your chest, so there's really no reason to aim for the head.

@Beefster if the target is wearing plate armour an arrow might not penetrate at all but an arrow to the head has a very good chance of knocking the target out even if it bounces off. Not that they actually aimed for the head though.

i mean like slingshot or darts, heck throwing the rock barehand directly with the horse momentum speed probably devastating enough, also since you want to make them into horse archer wont they pretty much wont miss from their shot anyway, since horse archer pretty much can get closer to their enemy to shot in short and safe distance, and not get caught due to their fast and maneuvarability even heavy charger wont easily caught up to them. although their warbow actually has stronger/similar draw weight with english bow though, dont get fooled by the size.

well javelin is good alternative, it may not as strong using crossbow or warbow but for this weak person it viable, beside it can get stuck to enemy shield to give more burden, also you can use it as lance substitute if you want to charge.

or if you think they are to weak to even lift a javelin theres also war dart. and before the confusion, at first the sling that i mention was not for cavalry, but slingshot may work.

Just a note, accuracy does not purely increase from having great eyesight. Accuracy comes from having great muscle memory, strong muscles and a lot of experience shooting the bow.

Place some of then inside "British Squares". The square keeps them safe from cavalry and heavily armed rapid attack and they can then target at very close bow range but well beyond what the square's footsoldiers can otherwsie do.

Is there a reason they aren't using crossbows?

The draw weights of english longbows required archers to spend many years of diligent training in order to develop the muscle to use them. You're not giving untrained creatures anything remotely resembling a war bow and expecting them to use it. Yes, lighter than a human war bow, but for a gnome that is still their equivalent of a war bow and thus requiring many years of diligent training in order to build the muscle mass required to be able to effectively draw it, and still that would only get them to being as powerful as a human hunting bow.