Standing Breech Shape Question

[Joe S]

The standing breech I have has flats that match the top five barrel flats, but the bottom of the standing breech is round where it matches the bottom three flats.  The round sections create a small (0.065”) lip. 





I have two questions:

1.  Why is the stranding breech round on the bottom?

Two possible reasons come to mind – maybe the barrel it was originally matched to was round on the bottom; or, perhaps when you inlet the lip, it helps reduce any tendency for the barrel to lever the tang out of the stock when the barrel is removed.

2. Shall I file the round section to match the bottom flats, or leave it as is and inlet it that way?

My plan is to put in a screw from under the trigger guard into the standing breech to help secure it. If I do that, I don’t see a need for a lip on the breech to help reduce levering force on the tang.  So, I may as well file the breech to match the barrel, and make inletting a whole lot easier.

[Joe S.]

If I understand this correctly wouldn't it make sense to file it to match.Easier to inlet and not as deep.

[James Rogers]

Here is a historical English 3rd quarter 18th century example. Noted London maker Joseph Heylin. Square bottom for a square bottom barrel. Notice the tit at the bottom of it going deeper in the bottom of the inlet. A pin goes cross ways thru to hold in the standing breech along with the tang screw.

[Joe S]

Thanks Jim.  That makes sense.  I don't have enough steel to run a pin through the lump on the bottom, but it's easy to weld some on.  Here's where I got the idea for a screw coming up from the bottom:

see replies #27 and #37 in
http://americanlongrifles.org/forum/index.php?topic=38964.25


So, now I have two good historically correct options.

Here’s the picture that goes with #37:

[James Rogers]

Yes, your arrangement should be great for a later period gun and make for a secure standing breech. I didn't know the period of the gun you were building. My mind just automatically goes to 18th century English guns : ) For sure, that same procedure was also used on wrist escutcheons and even to secure some early half stocks at the fore end. If there are 18th century English examples of this type of attachment on standing breech guns I don't know of them but could be possible. Always learning something new and there may be examples out there.
The thumbpieces I have seen secured that way had the screw also running thru a countersunk hole in an extended trigger plate.
So what type of gun are you creating?

[Joe S]

1760-ish English fowler.  Maybe the pin arrangemnt would be more correct for an earlier gun?

[James Rogers]

That's the way I would go as I have seen many examples of it on the type of gun you are making. Can't recall an example of a bottom screw on a breech.

[Joe S]

OK.  I'll file the bottom of the standing breech to match the barrel flats, weld on a tit and pin it. Your advice is much appreciated.

This will be a sort of Twigg inspired gun, mostly because that's the best set of photos I have.

[Mike Brooks]

Thanks Jim.  That makes sense.  I don't have enough steel to run a pin through the lump on the bottom, but it's easy to weld some on.  Here's where I got the idea for a screw coming up from the bottom:

see replies #27 and #37 in
http://americanlongrifles.org/forum/index.php?topic=38964.25


So, now I have two good historically correct options.

Here’s the picture that goes with #37:

I have seen this screw arraignment on an 1820's English SXS. I don't think it is appropriate for an earlier gun.
  Wait till you decide it's time to run a pin through that little lug. Hard little devil to hit the first time.....don't ask me how I know.

[Joe S]

Thanks Mike.  I was hoping you would comment.

I don’t think I’ll make a little nub like the one in Jim’s picture.  I know my limits, so I’ll make one twice as big.  I have Rase’s infallible drill jig, and my Pile O’ Toothpicks repair kit, so I’m ready for this project.  I don’t think it will take me more than two or three tries to hit it.

[Mike Brooks]

Thanks Mike.  I was hoping you would comment.

I don’t think I’ll make a little nub like the one in Jim’s picture.  I know my limits, so I’ll make one twice as big.  I have Rase’s infallible drill jig, and my Pile O’ Toothpicks repair kit, so I’m ready for this project.  I don’t think it will take me more than two or three tries to hit it.

Toothpicks, always in every good gunmaker's tool kit, and plenty of them! I'd be lost with out a bundle.