drilling and tapping barrels for breechplug low tech

[Justin Urbantas]

I saw these Nock pistols. Pretty similar.
https://www.skinnerinc.com/auctions/2760M/lots/11

[Daryl]

Good choice, though - 4 1/2" will keep them from being PROHIBS - HOWEVER ----- 

I think you should plan on making them 4 1/2" INSIDE length - that being from the front of the breech plug,

or you may find you are building prohibited firearms. Yeah - I know it's a stupid law.

With a 1/2" long (interior) breech plug, that will make them 5" in length overall.

My non-original .45 Deringer has a 2 1/2" bl. and it is classified as a prohibited firearm.

I do like the looks of that 'original' in the picture.

I was wondering where they would measure from on the barrels. If it is front to back, or if they poke in a ramrod, and measure the actual bore length. The picture of the original has a 4" barrel.

Quite likely they will be measured the same as for a Semi-Auto, with a pencil down the bore, marked and measured from the eraser to the mark.

[Justin Urbantas]

Good choice, though - 4 1/2" will keep them from being PROHIBS - HOWEVER ----- 

I think you should plan on making them 4 1/2" INSIDE length - that being from the front of the breech plug,

or you may find you are building prohibited firearms. Yeah - I know it's a stupid law.

With a 1/2" long (interior) breech plug, that will make them 5" in length overall.

My non-original .45 Deringer has a 2 1/2" bl. and it is classified as a prohibited firearm.

I do like the looks of that 'original' in the picture.

I was wondering where they would measure from on the barrels. If it is front to back, or if they poke in a ramrod, and measure the actual bore length. The picture of the original has a 4" barrel.

Quite likely they will be measured the same as for a Semi-Auto, with a pencil down the bore, marked and measured from the eraser to the mark.

Makes sense. I guess I'd have to go with 5".

[ddoyle]

Buy a tap with the same TPI but a smaller major diameter then your indended plug. Tap with that undersize one first. It will guide the full size tap that will do the bulk of the work. China will sell you taps of exc quality that are undersized.  One extra tap might make it work for you. If it was me I'd take a hard look at Machinery's handbook and find a better alternative then 3/4-16. Add more TPI and the job will go much better.

Using the undersize tap first makes it 100X easier.

[bob in the woods]

Low tech here. I've breached a few barrels, [ some home made ] with just a brace and drill bits. and files . Taps/bottoming taps etc also used in the brace. I'm in no hurry, and it's worked out very well .

[JCKelly]

1959 - 1969 I tapped & plugged about three barrels with no lathe, no drill press. Worked for me. Start with undersize tap, finish with a bottoming tap. Do use tapping fluid. No power tools, go slow.

[Justin Urbantas]

say you were to go with 3/4x16 thread for the breech, which size would you start with?

[Justin Urbantas]

I wonder if one size smaller would work to get it started as long as it was 16 threads per inch?

[ddoyle]

Justin,

To decide what is right for your project get a copy of Machinery's Handbook and look at the thread tables.    You do not need to limit yourself to 16tpi it could be 14, 18,20 depending on what you decide will work and what taps you want to buy.   

Your first tap needs to make a cut in the over size hole- to get an idea of how much it will cut look at the engagement tables in Machinery's handbook.  Machinery's handbook is widely available for 10 bucks. Older editions are better for a blacksmith like you.

[Justin Urbantas]

thanks. I'll look on Amazon