Where are you from in Africa? You ought to have plenty of good bow wood in most areas. If SA, there is loads of hackberry, honeysuckle and chinese elm. Evidently most are invasive, so you ought to have a pretty unlimited source of wood. I lived in Nigeria for some time when younger with family friends and I was always impressed with african hardwoods. Don't know how easy they are to come by now, but the group loves to see what people do with local wood as well that we've never seen before. Ash is a known for its variation. Also, ash isn't normally sorted well according to species at lumber yards, so it is difficult to actually know what species of ash you are getting. It matters a great deal. Ash has its issues to begin with, so getting a nice dense piece of the right species is an important factor in making a good bow out of it. Roasting it is also another consideration to help it deal with compression issues. A side thought as far as tools go, oftentimes tools are "trained" as you use them with only certain materials. So, if you are always cutting the same sort of wood, the tool literally becomes accustomed to working this type of grain and throwing a different grained wood in there can cause issues. A lot of sawmills have this issue with pine since the random piece of compression pine that is wound to end up in there often will wreak havoc on their machines due to the change in density. I know that sounds weird, but most machinists are well aware of this. Ash has long fibers which is one reason it makes a good backing wood. This is also another reason why it becomes like condensed grass for your saw blade. You need sharpened or new blades for woods like hickory and ash. So, it is likely the difference between bullet wood and ash you are experiencing are due to the grain of the wood. I am pretty sure bullet wood is more dense than ash, but don't quote me on that. The more you work with bow woods (or just wood in general) the more you realise that you need the right tool for the wood you are using because they all react differently to different tools. Like draw knives, the quintessential tool of the bowyer. You can't use it well on certain woods without it tearing out fibres and threatening your project. All the ash I used in the past, I used a farriers rasp with after shaping it with a band saw. Later, I decided it made a much better backing than bow. As a backing it is exceptional. As a bow, not so much.
