Breech Plug Contact Points

[silky]

Evening,

I have a barrel with a manufacturer-installed breech plug.  Can you guys help me with two questions?

1). If there's zero contact between the faces, I need to ignore the manufacturer's witness marks and properly seat this thing, right?  The face of the breech plug is not making any contact at all with the face on the inside of the bore, and measurements show the plug to be about .02" short.  I probably answered my own question here because it's so obvious, but being pretty new to building, I have a major mental roadblock trusting myself and not that nice alignment mark placed by a professional barrel maker!

2). Taking a look at these pictures, is the face on the inside of the bore in good shape or is there some damage there?  It's a barrel I bought new from TOTW and I haven't done any work to it yet.  Having watched/read a number of videos and tutorials tonight, it strikes me as not looking too good.  But again, I don't have a lot of experience in this arena.

I appreciate your insight and help.  Everything I've read here says to take the time to do this part right... want to make sure I do!

- Tom

[rich pierce]

Looks like a Colerain barrel. It’s not unusual to see some edge that needs to be de-burred. Happens often. If the plug is not touching and is 0.020” off then I’d pursue getting another barrel if you don’t feel confident to fix it.

Let’s say you want to tackle it. If it’s threaded 18 threads per inch then each full turn is about 0.055”. That is about 0.007” per flat on an octagon, so 3 flats should snug it up if your plug is 0.020” shorter than the barrel threads. You’d need to remove from the face of the barrel of course to get it turned in further. If you’re careful, good with files, use transfer material, and go slowly it is very do-able. The Colerain stamping on the bottom of the barrel is very shallow and will file off easily so nobody will know it’s been rotated.

Other methods may be suggested but this would be my approach.

[Curtis]

I would paint the plug face with a blue or black sharpie marker (cover it well), then screw it in and tighten it to the mark.  Remove the plug and then check the face to see if there is good contact around the edges of the plug face.  If so, the metal to metal contact will remove the sharpie color where the metal meets.  If all or most of the color remains, it means that there is not much or any contact.  Dykem will work for the purpose as well.

Just my 2 cents worth.

Curtis

[EC121]

You nee to fit the breechplug as Rich suggested.  In the "old days"  All barrels(except maybe Getz) needed the plug fitted(if they even came with a plug).  It was SOP to fit them.  There was usually enough metal standing proud to pien it down once the plug met the bore.  These new barrels have the excess plug metal ground flush with the flats.  It makes it harder to fit the breech end tightly

[jrb]

If indeed, you suspect  it is not properly fitted, and the barrel has witness marks chiseled in, showing they supposedly properly fit the plug, then, i'd phone the maker and tell them i wanted another barrel with a properly fit plug. It won't be fun, but if it doesn't seat then it wasn't properly done by the maker (assuming they sold it as a fit breechplug barrel). in fact i'd post this problem on every other of the many rifle building forums on the internet, if your breech isn't fitted and was sold as "fitted". let future buyers know.

[silky]

Thanks for the help, guys.  Scott from Colerain was nice enough to take a few minutes and discuss this with me on the phone today, as well.  He said the breech plug needed one more full 360-degree turn in order to accomplish the proper breeching while maintaining the bottom flat as the bottom, so I've been working on that today.

Rich, your math was dead-on, as the plug bottomed out on the third flat!

I'm close, within 2 flats of getting this all the way around, but every time the plug bottoms out, it shows not only contact but also appears to be deformed.... hopefully the pictures show what I'm talking about.  Any ideas what's going on here and what the fix is?  Or is this normal?  I've been doing my best to remove chips and filings so as to keep the threads clean.

Again, I appreciate your time in helping me understand this and achieve a safe seal.

- Tom




geojson io

[rich pierce]

You’re doing great. I’d de-burr the face of the plug and keep at it. You’re almost there and it will be breeched better than most barrels.

[flinchrocket]

Also, as you get closer you will need to remove some of that first tread. A little transfer color will help there too.

[silky]

You’re doing great. I’d de-burr the face of the plug and keep at it. You’re almost there and it will be breeched better than most barrels.

I appreciate it!  When I de-burr the face (while filing it to continue the process of getting it breeched) then bottom it out again in the barrel, the plug comes out with that distortion every time.  Is that normal?

[rich pierce]

Yes I’ve experienced that. The threads at the shoulder are incomplete.

[Not English]

Silky, it use to be common practice to run a bottoming tap down the breech. I still do it and prefer to fit my own breech plugs. Running the bottom tap down to cut the last thread or 2 in the breech will help  take care of the metal movement you're seeing. You will need to  do the filing of the breech plug thread as Flinchrocket pointed out

[silky]

Evening!

Gentlemen, thanks for taking a few minutes to help me out with this.  The end result is a breech plug in contact with the shoulder all the way around and a seamless flat on top. 

I filed the thread as you guys said to and that distortion on the face of the plug stopped occurring.

Again, thank you.

- Tom