From The Comanche Empire, by Pekka Hämäläinen (Yale U. Press, 2008), pp. 72-73:
Initially, in the early eighteenth century, Comanches had been largely cut off from the burgeoning trade in European weaponry in the continent’s center. Large quantities of guns, lead, and metalware flowed onto the grasslands from the north and east, from the French and British outposts in Canada and the Mississippi valley. In contrast, the Spaniards in New Mexico and Texas were reluctant to sell guns to Indians, fearing that those guns might be turned against themselves if the Natives allied with France or Britain for an attack against Spanish colonies. This disparity in the pattern of diffusion gave the northern and eastern plains tribes a decisive military edge—something that Comanches painfully learned in their early wars with the Pawnees and Osages. But the rise of the upper Arkansas trade center allowed western Comanches to break free from the gun embargo. By channeling large numbers of horses to the northern and eastern Great Plains, they managed to create a substantial inflow of firearms. Alarmed Spanish officials reported as early as 1767 that the western Comanches were better armed than Spanish troops.
Before long, in fact, western Comanches accumulated such quantities of guns and other manufactured goods that they could start exporting them. Domingo Cabello y Robles, governor of Texas, reported in the 1780s that western Comanches sold guns, powder, balls, lances, cloth, pans, and large knives to their eastern relatives in the Texas plains, who in turn supplied western Comanches with horses and mules, some of which were traded to Wichitas, Pawnees, Cheyennes, Kiowas, Kansas, and Iowas. Moreover, in a reversal of the typical forms of colonial trade, western Comanches started to sell guns and other manufactures to Spanish New Mexico. Such a trade was first mentioned in 1760 by Bishop Pedro Tamarón y Romeral who wrote that Comanches sold muskets, shotguns, munitions, and knives at Taos. Fifteen years later the trade had become a routine. When visiting the town’s summer fair in 1776 Fray Francisco Atanasio Domínguez was struck by Comanches’ export stock, which included tin pots, hatchets, shot, powder, pistols, and “good guns.” The gun trade, Domínguez noted, had become established enough to be based on fixed rates. “If they sell a pistol, its price is a bridle.” In exchange for the precious manufactured items, Comanches received special equestrian and hunting gear, such as bridles and belduques, broad butchering knives, which were available only in New Mexico. Western Comanches, it seemed, were creating a multilevel commodity flow that furnished them with imported staples, such as maize and horses, as well as with more specialized manufactured products.
But the inverse trade in guns and other European commodities only hints at a much more profound shift in Comanche-Spanish relations: western Comanchería had begun to replace New Mexico as the paramount economic, political, and military power in the Southwest.