Could be Spanish, could be some group traveling west and from where you are, west meant Comanche. Before that other tribes. Defended themselves or test fired the gun? No way of knowing I guess. Really special find though. I have a small one, maybe an inch or less in diameter. Was told it was Spanish "shot"(like buckshot). Cannon was loaded with many and then fired. Sort of like a shotgun. Found it in a field on the edge of San Antonio. How, why? Don't know. There are a lot of relics in Texas. You found a great one...