Metric breech threads

[msellers]

Ok, so if this question is in the wrong section please move or delete. I have an old barrel I asked about recently in a different section, that from all my measuring and test fitting is a metric threaded breech. Based on the thread chaser that easily fit into the breech it appears to have been tapped for a m18x1.5 thread. Has anyone seen this before, or know of a breech plug with this threading, I haven't located one in my searches. I am guessing that I will have to build one to this spec, but wanted to reach out to you all first.
Thanks in advance,
Mike

[45-110]

way more precise to use a metric thread gage to verify the pitch, not a thread chaser.

[M. E. Pering]

Are there any other markings on the barrel?

[msellers]

No markings at all. And I verified with a metric thread pitch gauge as well. But I only have the crappy one with my cheap die set. Will try and track down a better set, and verify again

Mike

[Bob Roller]

No markings at all. And I verified with a metric thread pitch gauge as well. But I only have the crappy one with my cheap die set. Will try and track down a better set, and verify again

Mike

Possibly a pipe thread of some kind but aren't they usually tapered?
11/16 is about the closest fractional size I can see in the "Special Thread"
taps of Travers Tools catalog.

Bob Roller

[rich pierce]

Is the “old barrel” pre-1860 or pre-2000?

[msellers]

Is the “old barrel” pre-1860 or pre-2000?

I wish I knew better, it is definitely pre 2000. It has some pretty heavy corrosion putting towards the breech end. However, the threads and crown appear more recently cut.
Mike

[DutchGramps]

This  is most probably Metric fine M18x1,5, used in Europe after the French revolution