jenkins-script-console.groovy

// delete build history in range and reset build number

fullJobName = "full/job/name"
start = 1
end = 10
nextBuildNumber = 1

item = Jenkins.instance.getItemByFullName(fullJobName)
item.builds.each() { build ->
  if (build.number >= start && build.number <= end) {
  	println("deleting build: " + build.number)
    build.delete()
  }
}

item.updateNextBuildNumber(nextBuildNumber)