I have heard that former Chief Ranger Nelson's gun business involved the questionable use of special "law enforcement discounts" to buy and sell firearms to some non law enforcement persons. Also that government employees and vehicles may have been used to support this scheme, if true a likely conflict of interest.
The Bowen Ranch area is well within the county's "Shotgun only" firearms restriction ordinance, which Nelson would well know. If what you're saying is true about his shooting rifles out there, and a BLM fireman once told he witnessed the same thing, then he and whoever he was with were violating that ordinance.
As for his alleged DEA Central American exploits, this individual is known for his world-class embellishments and I would be suspicious.