Using configuration.application.artifacts will only provide you with the declared artifacts of that configuration. What you want are the actual artifacts of the resolved configuration, which is accessed via configuration.application.files or by configuration.application itself:
task show << {
configurations.application.each {
println it
}
}
// In project2
dependencies {
application project(path: ':war-project', configuration: 'archives')
}
// The war file is then the only element of the FileCollection
configurations.application