First breach plug install

[Big Bertha]

I'm just getting  going on my first project in several  years. I'm hoping  to end up with a Jacob Dickert looking rifle. I've built a Jim Bridger Hawken several years ago but this is my first ever breach plug install. I ended up with the plug tightening on the bottom flat instead of the top. I used a crescent  wrench and gave a firm "bump" My thinking  tells me that I now need to remove equal amounts of material from the inside of the plug and the backside of the barrel. Is that correct?

[JPK]

The end of the breech plug should seat against the end of the rifling, to do that the end of the plug need to be truly flat. It may help to place a nut on the threads to help you file a flat end.  This will allow it to seal the breech, and when that happens you will see a mark on the flat end of the threads. Carefully remove material from the barrel till the tang comes round to the top.

[David R. Pennington]

I use prussion blue and try, file, try, repeat until I get perfect fit against bottom of threads and tang aligned correctly.

[mikeyfirelock]

Check your depth of the breech vs the length of the breech plug threaded section and make sure that there will be contact both places when tightened.   I use the depth guage on my vernier calipers to check this in the barrel, and the caliper to check the threaded length.  If there’s a difference, then the longer one must be shortened to match.  You must also keep in mind that you must not only match these surfaces to seal the breech, but make sure the tang and top flat line up at the same time, which will require patient rechecking, refilling, and refitting.   It is NOT HARD TO DO………BUT IT DOES REQUIRE PATIENCE !     Just do it once and do it right and you’ll find out it’s not hard to do at all.

[Steeltrap]

It's hard for me to tell from your pic here, but where I have the arrows is that the edge of the breech plug face?  And the black around it is on the threads of the plug?

[Big Bertha]

Yes that is the edge of the breechplug face. The black is inletting black picked up from the inside shoulder of the barrel.

[Steeltrap]

If you look at this pic, where I have the white circle (bumpy circle, but still) that should represent the size of your bore. (Not to scale of course). When you have that breech plug seated properly that surface on the outside of the bore, to the corner of the plug, should show black all the way around. Then you know you have a bore seal.

At this point, you need to carefully remove some tang metal (keeping it square) that will allow the plug to reach the bore inside the barrel.

Once you have that seal, then you determine if your flats align. If not, you will need to carefully remove metal from the bottom of the plug until the tang aligns with the barrel flat.

As stated above, you should measure the distance between the end of the barrel and the bore. I always use the plunger end of my Dial Caliper for this.

So, you may want to measure this bore depth, and also the length of your plug. They should (hopefully) be very close. But this will provide you information as to how much more metal you need to remove.

[bptactical]

You’re going to want a more substantial vise IMO when you go to pull it up for keeps.
If you want the math of it- a 16 pitch(assuming that’s what you’re working with) thread advances .063” per turn. So to get your 180 degrees you need to remove about .0315”.