The barrel has a narrow portion that is cut down just after the gas block and under the handguard retainer... The barrel press simply uses this larger shoulder on the barrel to support the barrel when you press. It is a simple design but works very well.
Xebec is a full time graduate school student and he makes these in his spare time... I think he is getting busier with his classes so less time for "playing"...
Actually I do have a couple for sale right now, and have been trying to get caught up on the e-mails. E-mail me at xebec79407@lycos.com if you are interested.