I understand the concept of why you would want this done, but what is actually involved?

I watched that and about 4 other videos today. Finding the centerline of the receiver i get. Squaring the front of the receiver I get. Squaring the front of the locking lugs I get. Lapping compound for the bolt where it meets the locking lugs... Check. Squaring the front of the bolt. Yup.

 

I have no idea what exactly they do with the threads though. It looks like they just go back over the with a new tap

I love Potterfield gunsmithing videos.  

I have no idea what exactly they do with the threads though. It looks like they just go back over the with a new tap

The threads get re-cut, single point, on a lathe.  All indicated off the centerline of your bolt raceway (God I hope I'm saying this correctly so I don't look like a complete ass)  If you simply re-tap them it's a waste as the barrel will go in crooked in relation to the squared up faces of the receiver and bolt.  

 

It takes a good bit of training to make it right.  It's a beautiful thing when done correctly.

That's what I thought. I guess I'm having a hard time understanding that visually in my head. Are you making the opening bigger?

The threads get re-cut, single point, on a lathe.  All indicated off the centerline of your bolt raceway (God I hope I'm saying this correctly so I don't look like a complete ass)  If you simply re-tap them it's a waste as the barrel will go in crooked in relation to the squared up faces of the receiver and bolt.  

 

It takes a good bit of training to make it right.  It's a beautiful thing when done correctly.

Chris,

 

I believe the threads aren't recut.  Instead, they chase them, which is just running the tap and making sure there are no high spots or tight/bent threads.  If you recut threads, you are removing much more material and would have to make the opening larger, which needs a larger diameter threaded barrel end.  If not, the barrel would be too loose when screwing it on.

 

Hopefully, Mike/Tier One or another gunsmithing expert can confirm this?

Many ways to skin the cat. Whether someone recuts the threads or recuts the action face square to the existing threads. Square is square. Many old school smiths, including pws builders don't believe in recutting threads. Too many people mimic what they see on youtube and copy cat the nonsense.