Smithy 3 Jaw doing the work of a 4 Jaw....Mosin Nagant barreled action

Just a follow-up on the last video discussing the lathe spider for the Smithy Granite 1324. Shows setup in the 3 jaw to get a rifle bore dialed in. Was going to thread the barrel but there isnt enough meat at 20" to cut the 5/8-24 threads.............ahh the Mosin will only get a crown.