All center fire ammunition can be reloaded, including brass, steel and aluminum. It is just a matter of skill and equipment. However, just because it is possible to reload all kinds of bullets doesn’t you should.
Aluminum, for example, is the softest metal used in ammunition. In fact, it is generally too soft to be used safely as a reload unless you are both truly meticulous and desperate for the bullet.
Steel is harder than aluminum, but it still presents challenges for reloading.
The material is hard to reload without cracking the metal and compromising the safety of the shot. Steel rusts quickly, meaning it has to be dried immediately after shooting to be reloaded. It gets dirty easier than brass and can also stick in the chamber, damaging your gun and potentially endangering you. On the other hand, steel is less expensive than brass.
Of the three metals, brass cases are preferred by reloaders. Brass cases are more elastic, which helps them go through multiple reloadings just fine. This enhanced durability plus the wide availability of brass makes it the safest and most popular metals to reload.
One note for all types—pay attention to the primers. Berdan-primed bullets are less expensive than boxer-primed bullets, but they are more difficult to reload. Thus, you’ll want to consider both the sticker price in reloading and the price of your time dealing with more time-intensive reloading procedures.