issue with breech plug

[bjarard]

I don’t see how you can get 360dg contact with shoulder since the threads are helix. Is 360 expected??

 

[chorizo]

I don’t see how you can get 360dg contact with shoulder since the threads are helix. Is 360 expected??

Think about that...both threads are helix

 

[bjarard]

Think about that...both threads are helix

Any advice for getting transfer 360 or is it not necessary.

 

[chorizo]

Any advice for getting transfer 360 or is it not necessary.

Yes, it is necessary. If by hand, very slowly, very methodically, and VERY, VERY little removed at a time.

Plug and face should contact at the same time.

 

[bjarard]

Yes, it is necessary. If by hand, very slowly, very methodically, and VERY, VERY little removed at a time.

Plug and face should contact at the same time.

Is it a matter of filing the high (touching) points of the plug face perimeter.

 

[chorizo]

Is it a matter of filing the high (touching) points of the plug face perimeter.

Sort of, you have to make sure that the barrel face is square. If the barrel face isn't square you will never get full contact. It is a back and forth until everything touches

And both have to happen at the same time.

But I have only done one, so I am no expert. Hopefully others with more experience will chime in.

 

[SDSmlf]

Not when the sights have already been drilled and tapped….

We learn from our mistakes…

Gives you the opportunity to practice on each flat until the one with the sights on it comes up to 12 o’clock.

 

[smo]

Gives you the opportunity to practice on each flat until the one with the sights on it comes up to 12 o’clock.

Until you run short of threads on the plug..
I was down too 5… just over 1/2”.

Once I got the plug too mate with the barrels inner ledge.
I found a bronze washer and ground it the the proper thickness then test fit and marked the flats on the washer with a Sharpie.
I then removed the washer a ground the edges close too the Sharpie line , reinstalled washer and thighted the plug into place..
Finished hand filing the washer too match the barrels flats..
It was a job, but it worked.

 

[SDSmlf]

Until you run short of threads on the plug..
I was down too 5… just over 1/2”.

More than one way to skin a cat as they say. Realistically, let’s say the plug has a TPI of 16, a full revolution is only .062”. If you had ‘just over 1/2” ‘, another turn would have made no functional difference. But nothing wrong with washer if it works.

 

[IanH]

That copper spacer looks neat, almost as if done for its own sake and not a workaround.

 

[le125verne]

I'm setting up the breech plug on a round barrel. It was screwed in tight so I backed it out to apply inletting color ...screwed it back in and it appeared there was no transfer. So I proceeded to remove a little of the tang that butts agains the barrel rear. Screwed it back in and it stopped...but now with a small gap where I removed some of the tang. Backed it out again and ...again...no transfer??? I would think it should act like a giant screw...once any impedence is removed it should screw all the way down upon the shoulder.

I then screwed the plug back in and ran a straight rod down the barrel till it bottomed on the plug face...then clamped into place. Removed the plug and the end of the rod is very slightly ahead of the shoulder...indicating the plug is going all the way in.

Why am I not getting any inletting transfer?? it looks like there is some inletting transfer on one of the last threads...but I thought it needs to transfer to the larger flat area at the bottom. the plug does have a slight bevel if that matters.View attachment 253536View attachment 253537View attachment 253536

Question; Is there any "shoulder" near the tang that is hitting and thus not allowing the breach plug to screw 100% of the way in?

 

[GREENSWLDE]

As was said Bottoming Taps have a slight taper on the end thread.
I have Two bottoming taps. One still has the taper. The other I have ground the last two threads Off.
This gives full thread depth to the bottom of the thread in the tube. Makes bottoming out a lot easier if the plug is machined to full thread square end.. If you do this Be vey light fisted cutting the last thread . You dont need to chip the fine half or quater thread end of the tap.. A few more Plug fittings will help after some years...It also helps if the last thread up against the tube end is under cut to full depth.. O.D.

 

[bjarard]

I finally got a 360 contact and the tang is air tight up against the barrell. Final question…5-6 remaining threads OK?

 

[GREENSWLDE]

Air tight it may be ?? Is it Explosion tight.Time will tell.O.D.

 

[bjarard]

Air tight it may be ?? Is it Explosion tight.Time will tell.O.D.

The tang portion. It’s cosmetic.