Thompson center inter changability

[Gcs71]

Exactly how are the “flats” measured?

 

[deerstalkert]

Exactly how are the “flats” measured?

take your calipers and slide the jaws down on each side of the barrel. that is across the flats.

 

[necchi]

Exactly how are the “flats” measured?

"Flat's" refer to octagon barrel. The measurement is from one opposing side to the other, as exterior.
When dissected with a micrometer the differences will be noted in or near 0.0625 of variations of 1" vs 15/16".
Anomalies of manufacture within a few thousands are common,, but a 1/16" is commonly measurable..
Ask your local Cabinet maker or finish carpenter.
In my experience, when a comparable barrel is found to fit the stocks channel,,
The major issues are the tang/hook fitment of the existing components and proper tension of the lug key.
Folks have been swapping out the T/C parts for years,, and that's the trouble and/or challenge.

 

[Gcs71]

another question is, what does it take to remove a breech plug? Is just simple standard threading rules? or Are these best left alone?

 

[longcruise]

Removing a tc breech plug is best done with a special tool. Actually, there is one for sale in the classifieds.

It also takes a wrench to slide over the tool. I had one removed and reinstalled by a Smith and it was quite a tight fit. We went to his machine shop and he placed the barrel in a vice and slid the tool on. Then he adjusted a huge crescent wrench to the tool and literally bounced on it with his full weight to get it started!!

This wasn't unusual. TC installed all of their breech plugs with lots of torque.

My advice is to avoid doing it unless absolutely necessary!

 

[Bad Karma]

You’ll need a stout bench vice. 4” harbor freight vices need not apply. I spent the 50 bucks for the Rice Barrel company vice jaws, then the TC breech plug wrench. I used my corp stop flat jawed wrench to grab the breech plug wrench and hauled away on it. Proper tools make it easy but yes, TC used a lot more torque than necessary.