Order of operations, Barrel Threading.

[msinc]

M1917/pattern 1914's thread right up to the shoulder, I believe 03's do as well. Been a while since I touched a Krag barrel.
View attachment 1098848 View attachment 1098849

Kinda looks like that one might be centering on the very breech where there are no threads. The threads themselves will do it, but they have to be properly sized to each other {receiver and barrel that is}

 

[Cloudrepair]

Usually, but with a square thread not exactly...it depends on what you are "aligning"...if we are talking about the chamber/bore centerline to the bolt face when using a square thread then it is this unthreaded portion of the tendon that "aligns" {centers} the barrel to the receiver.
If some of these guys weren't so bent on calling out a simple mistake that had little to do with the point they would have realized that I am their "friend".....for those of you that caught the mistake, thank you, I have corrected my post. Endless apologies, a thousand pardons..... See photo of Garand tenon below, sorry fellas, I don't presently have a Springfield 03 or Garand receiver to photo and post..... View attachment 1098844

I have turned many square threads and acme threads and variations just not on barrels but they all seem to have a centering section on the threaded connection that centers it a long with the shoulder on the connection.
Because of this you do all work possible in the setup to insure concenticity when assembled. When you are making a coaring bit and your work doesn't align true it has a chance of ringing out, witch would mean the offset cutters may fall into the groove of the cutter ahead of it and it will stop the drill head from cutting and then you have problems.

 

[Doug Beach]

I just did a 1917 Enfield, removing an arsenal barrel, and the threads went all the way to the shoulder.

 

[spitfire_er]

I cut 1/3 to 1/2 of a thread off the end of the barrel which looks cleaner, and doesn't leave a sharp edge on the corner of the barrel. I've done it both before and after threading. Each barrel gets fit to each reciever and they are all different sizes.

Between the lug abutments and the back side of the thread in these receivers isn't always true. Taking a guess but they probably rough bored the reciever casting to get it roughed out, then came in with a thread cutter/tap of some sort to get proper threads.

Point being I would never personally rely on that little spot at the breech end to try and center anything. Tough enough working with a 100 year old military mass produced receiver.

 

[Cloudrepair]

From the looks o

Usually, but with a square thread not exactly...it depends on what you are "aligning"...if we are talking about the chamber/bore centerline to the bolt face when using a square thread then it is this unthreaded portion of the tendon that "aligns" {centers} the barrel to the receiver.
If some of these guys weren't so bent on calling out a simple mistake that had little to do with the point they would have realized that I am their "friend".....for those of you that caught the mistake, thank you, I have corrected my post. Endless apologies, a thousand pardons..... See photo of Garand tenon below, sorry fellas, I don't presently have a Springfield 03 or Garand receiver to photo and post..... View attachment 1098844

From this thread and the other pics I would think that the only thing trueing the chamber with the receiver is the shoulder, although it is Important to have concetricity it may be more important to have parallel and perpendicularity to the reciever, that is achieved with the shoulder in this case. And it is probably all that was necessary at the time for its purpose

 

[Will Henry]

Although a square thread does not generate the self centering forces equal to a vee thread, it still has some due to the pitch of the thread. In other words, a set of circumfrential square grooves would not center under load but a square thread will; just not quite as positively as a vee. Nonetheless, on match rifles which I have built on P14's, I cut the threads with no clearance and lap them in. Ultimately, it is the loading of the threads by the shoulder contact which centers the barrel. If the shoulder and /or face are not square, no thread will center perfectly. A coned mating surface at the the shoulder/face is probably the most rigid connection but measurement and headspacing is problematic.
I have come around to thinking, perhaps, the right time and method to cut the threads is on centers after the barrel is chambered. I've done a bunch this way and have been pleased enough with the result. WH