They tend to expand well and are reasonably accurate and inexpensive to practice.
If you can afford them, try also the Predators.
AND: Practice, practice, practice!
Use this target to get a good grasp of the location of the Medula Oblongata on different critters:
Also for the record, here are other critters:
Hit them there and it's "lights out".
HTH
Un Abrazo!
H�ctor