T/C New Englander Breech Plug Thread Size

[TGJaeger]

Title says it all. Does anyone know the thread size for the New Englander breech plug?

Thank you in advance for any and all help!!

 

[Scota@4570]

Probably 9/16 x 18TPI.

Advice? Unless you have a real barrel vice and a plug wrench that is made for that plug leave it alone. Improvised tools will ruin the barrel and plug.

You can not buy a replacement plug with that thread size. The generic replacements are 5/8 threads if you can find them. I had to make the plug and tang from scratch on a Senica I rebarreled.

 

[Zonie]

The information I have says the Thompson Center New Englander came in .50 and .54 caliber.

The bore must go all the way thru the barrel in order for the rifling cutter or button to be used so, whatever the breech plug size is, it's minor (smallest) diameter must be larger than the size of the rifling grooves. A TC .54 Hawken uses rifling that is .005 deep so, adding .54 + .005 + .005 = .550 diameter.

That makes my guess a 5/8-18 UNF thread. It's minor diameter is .565-.578 so, the clearance will be .015 to .028 .

I don't gurentee that the thread size is a 5/8-18 though. Track of the Wolf shows both a 5/8-18 thread and a 11/16-20 threaded plug for a TC barrel that measures 15/16" across the flats.

https://www.trackofthewolf.com/List/Item.aspx/667/1

 

[TGJaeger]

Gentlemen, Thank you for your thoughtfulness and kind replies. I find it really interesting and at the same time frustrating that S&W/Thompson Center will not sell replacement parts for their firearms. I realize that their machinery, personnel etc are no longer in place but not being able to purchase even basic repair parts is aggravating .

 

[bptactical]

I would guess a metric thread.

 

[Pete G]

Gentlemen, Thank you for your thoughtfulness and kind replies. I find it really interesting and at the same time frustrating that S&W/Thompson Center will not sell replacement parts for their firearms. I realize that their machinery, personnel etc are no longer in place but not being able to purchase even basic repair parts is aggravating .

Try to find parts for a Hudson automobile

 

[Scota@4570]

OK, my bad on the smaller barrel. My recollection is that TC used bastard threads on all their guns. You'll have to remove the plug to see. Some TC's are super tight and some are not. My recollection is that the clocked the plug by brute force instead of actually fitting it. A mentioned unless you use a real barrel vice and properly fitting plug wrench, major damage is likely.

The TC factory was burned down. All the parts were destroyed.

Why do you want to remove the plug?

 

[Scota@4570]

Update:
I found my ca. 1975 TC hawken flint kit gun breech plug. It is 0.680" x 20 TPI. That is close enough to 11/16" x 20 TPI for me. So they were an odd ball thread.

 

[TGJaeger]

Hey Scota,
Thank you for working on this! I do have a barrel vise and wrenches but the person who owned this prior to me had little respect for his property. He must have fired it and either left uncleaned else He tried to clean with something very corrosive. I am thinking about having Colerain make one of their 20ga. turkey barrels for it, but I’ve no idea how bad the plug is corroded. Also, not sure if I can find a new one that will match the New Englander patent breech.

 

[Scota@4570]

Bobby Hoyt can save the old barrel.