Swamped octagon rib fitting

[Scota4570]

I want to do a more dainty version of the Kunz half-stock recently sold on James Julia.  I want to make a rifle with similar Kunz features but scaled down. 

https://jamesdjulia.com/item/lot-2387-outstanding-jacob-kunz-flintlock-half-stock-rifle-48490/

That rifle is pretty chunkie, the barrel is pretty big across the flats.  I want to make it's little brother.   I want to go with a light swamped barrel.  The barrel I am looking at is 0.71" at the small of the waist.  I calculate I will have to take about 0.030", or about 0.015" per side off of the rib width the thinnest point of the barrel.  I think if I draw file carefully I can make the rib width follow the barrel flat. 

http://www.pagetutor.com/octagon_layout/

Can anyone comment on my scheme?

[deepcreekdale]

Looking at that picture is sure looks to me like a tapered barrel. Plus it looks like the rib has a taper from the back to the front as well. That would be even lighter than a swamped one.  It is a beautiful piece though.

[Daryl]

I'm pretty sure I am seeing a swamped barrel.

[Scota4570]

I'm pretty sure I am seeing a swamped barrel.

Hard to say, tapered or swamped.  One of my ideas is to cut the flared portion off the muzzle of a very long barrel.  I was also thinking a half octagon would look really nice. Unfortunately suitable ribs are hard to find.  I want to keep it long and svelte though. 

I studied the photos of the original over the weekend.  The breech portion scales to be about 1 3/8" across the flats.  That might explain how the lock with the step down for the pan works on the original. 

In any case I cannot really copy it.  I just plan on using it as a general guide and use other known Kunz features as I feel the need.  Kunz was very stylistically diverse on what he made.  He also made a lot of very different types of guns.  I find his work intriguing. 

[FALout]

Maybe you could use a hollow rib, narrow it down as needed and then cut/grind the height down since it will get taller as you narrow it. 

[Scota4570]

Maybe you could use a hollow rib, narrow it down as needed and then cut/grind the height down since it will get taller as you narrow it.

Unfortunately those are "unicorn" ribs, if anyone actually sells them I'd like to know.  I think it would be better for a long barrel of a rifle I want to keep light. 

Scot

[Kevin Houlihan]

Scot
Muzzleloader Builders Supply has hollow ribs in their catalogue for $30. http://www.muzzleloaderbuilderssupply.com/
Part # RIB-HOLLOW - Hollow under rib
Kevin

[deepcreekdale]

After reading Daryl's post, I think he is right. I put a straight edge up to it and there indeed might be just a bit of a flare at the muzzle. Modern barrels of course, tend to have much more taper and flare than originals. Personally, I love half stocks with long barrels and this one sure fits the bill. Might take some file work to reduce the flare in a standard barrel if you don't want to go the custom route. Sure sounds like an interesting project. Finding an underrib long enough might be hard, the ones available are usually 24 inches max. Would be an interesting welding job to join 2 of them but not impossible by any means. Now you have me tempted to try something like this. Looking at that toeplate is enough to get me excited. That is beautiful architecture throughout. Please keep us posted on your progress.

[flehto]

why not use a hickory  under rib......light and much easier to shape.....Fred

[Scota4570]

The solid ribs can be had up to 30".

How would I pinch the hollow rib in a smooth consistent way?  Make a device with opposing sealed bearings that I could bring together with a jack screw?


A wood rib does not seem like it would hold up to me.  Also I do not like to drill and tap holes in barrels, especially thin barrels. 

S

[JBJ]

The last wood under rib that I saw was on an old rifle and was pinned to small underlugs. The lugs were handled in the typical shallow dovetails in the barrel. It was all neatly done and seemed to have lasted quite well for a LONG time. I suppose that the underlugs could also be soft soldered to the barrel and completely hidden by the rib.
J.B.

[Scota4570]

I thought of that after I posted.  Thin T-shaped lugs and brass pins would work well. 

I am warming up to the wooden rib idea. 

How about making the rib?  Make a shooting board and contoured planes?  Like bamboo flyrod construction?  I have no local  sources of hickory.  How about buying a couple of large ramrods and work them down? 

Finally how to securly attach ramrod pipe?  Should I leave a split tab in the pipes and put them around the same lugs that secured the rib? 

I tend to works out every detail, in  my mind,  before I start a build.  Then I build it on paper and make 1:1 scale plans.  I usually have to reinvent something anyway.  I find the planning stages rewarding too.  It is like solving a puzzle. 

[eddillon]

I have tried to make a sheet metal rib conform to a swamped barrel.  I gave up.  I decided to not destroy a perfectly good rib. pinching the sides not only raises the height but makes the rib bend longitudenally.  Went with solid rib that matched the flat at the waist of the barrel.  Hard to notice the difference between the rib and the rest of the bottom flat.  Don't have any photos of the finished gun.  At the time I didn't document with photos.  Foolish decision.