A heroin addict who stole guns from his father’s Beaver County gun dealership and a friend who helped him have both pleaded guilty to federal gun charges and are likely headed to prison in the spring. Timothy Brown Jr. of Rochester, whose father owns John Brown’s Armory in that town, has admitted that he stole more than 50 guns from the store and sold them to drug dealers for heroin. His accomplice, Daniel Nolder of New Brighton, also an addict, pleaded on Tuesday to possession of a stolen gun. Brown stole 53 pistols from his father’s store over seven months in 2014 and traded them for heroin. So far, 13 of the weapons have been recovered across the region.