Help with designing a round barrel?

[Canuck Bob]

I have an Euroarms of America Mountain style rifle I bought cheap, no pitting and in sound condition.  Typical Investarms half stock .45 with a 28" barrel percussion rifle bought cheap. I also have a 9" South Bend lathe that turns 36" between centers.

My questions revolve around using this collection of parts to make a LH flintlock rifle homespun kit.  The headstock draft of the lathe is 29/32 and the barrel is a 15/16" .45.  Rifle sellers make 13/16" barrels for .45 as what looks like a standard small sized barrel.  I found no 3/4" .45 barrels in a quick survey. 

Is 3/4" round Investarm steel barrel a safe size for a .45 flintlock rifle?  Or maybe a 13/16" breech straight for a few inches then tapering to 29/32 then a long taper to 3/4" at the muzzle. I will be shooting 50 paces range loads mainly but want it safe for hunting loads if I move it on.

I'm also considering a NW Trade gun octagon to round profile with 7/8" octagon tapering to the wedding bands. I'll have to work the current 15/16" breech with a file and have no idea if this is even possible for 6-8" of barrel.

I have very little into this rifle and am more than willing to use it as a disposable flintlock rifle building education for a much more correct build later.

Are there any round barrel flintlocks.  The only ones I found were big bore military guns.

[Goo]

I will make a few suggestions , you could take it to some one with a laser analyser gun get the read out and compare to tables for known steels.     You could contact the manufacturer to see if they can provide the info.  This will of course scare them to death if you tell them your plans.   Then thirdly you can make the alterations and proof the barrel with double charge and two firmly seated patched round balls as this seems to be the traditional method.     
In my experience you cant get many answers when you are outside the box you just have to proceed with your ideas and try your best to calculate and control the consequences.

[Mike Brooks]

I wouldn't go smaller than 13/16" at the breech then I'd taper taper to 3/4".

[D. Taylor Sapergia]

What is your purpose for making the barrel round to the breech?  My opinion is that if lightening the barrel is your goal, do it from the 9" mark on the barrel measuring from the breech.  Turn it into a round taper from a wedding band transition if that is what you want, or just start tapering and turning round from a few inches up from the breech, and forget the wedding bands.  Leave the breech a full 15/16", minus the drawfiling for finishing of course.

[Bob Roller]

Do you have a follower rest for that lathe? That skinny barrel will be a
"Get it right the first time"turning job.Also a live center for the tail stock is a must.

Bob Roller

[Canuck Bob]

Thanks everyone. 

Further research last night brought up a good point, flat profiles seal the lock/barrel faces from powder leaking into the stock inlet.  The attempt will be for an octagon to round profile.

The purpose is a first rifle build and learn as much about this lathe as I can.  I believe it has a follower but it is stored in my garage for a friend.  It is well tooled being the personal lathe of the local tech college machinist instructor.  Short term storage now seems permanent so I will use it for gun projects.  I once worked in a few production shop lathe operator jobs so I'm not a total newbie and a local builder has offered guidance as well.  I also rely and appreciate the help from forum members a great deal, thank you all.

The current plan (pipe dream?) is to use this donor gun to build a look-a-like NW trade gun without the cost of US sourced kits and tools not already in my possession.  I will order in either a Chambers or Hollenbaugh LH lock and maybe a trigger as the set trigger on this donor rifle really sucks as is.  The stock will hopefully be one whittled out of a nice local dried birch plank if I can figure how to make a RR hole with my tools. If not it will be a standard maple Pecatonica Trade stock with no channel or inlets.

This thread by David Rase, http://americanlongrifles.org/forum/index.php?topic=50862.0, really inspired me.  As well another thread by Mike Brooks about a rifle built simply (couldn't find link quick) influenced me as well.  It had no butt plate and modelled after an English rifle I think. 

Link to Mike's rifle, http://americanlongrifles.org/forum/index.php?topic=49363.0

[Mike Brooks]

Just for reference, you file a flat on the side of a round barrel where the lock mounts.

[Hungry Horse]

Most kit guns are button rifled. This process requires a steel nub on a rod being pulled through the barrel to literally iron the rifling into the bore, instead of cutting the rifling in with many passes with a cutter. Button rifled barrels from most barrel makers today are stress relieved, but those from kit guns, depending on their age, may not be. Turning an octagon barrel round, that hasn’t been stress relieved can be a problem. They sometimes go crooked when the supporting corners of the octagon barrel are turned off.

 Hungry Horse

[jerrywh]

 Profile it and proof it.

[Canuck Bob]

I've inventoried the South Bend and secured permission to use it long term.  It is well tooled with all OEM tooling I can forsee using except carbide cutting tools and coolant capabilities.  There is a follower and steady rest so there is no restriction to keep the barrel profile sized to the spindle draft.  I've never used either attachments so didn't realize the potential for muzzleloading machining.  It has the original tool holding system, sorry can't remember the proper name, and a large supply of HSS cutter blanks.

After careful research here the dimensions, particularly 3/4" round, I proposed were too light for an amateur's first attempt at contour machining for a .45. 

The next step is to insulate the shop, order in some reference materials for building, and researching octagon to round rifle history and appropriate flintlock builds.  Thanks again.

[Clark Badgett]

  It has the original tool holding system, sorry can't remember the proper name, and a large supply of HSS cutter blanks.

Rocker post?

[Canuck Bob]

  It has the original tool holding system, sorry can't remember the proper name, and a large supply of HSS cutter blanks.

Rocker post?

Works for me.  My memory seems to think it starts with L though. Edit rocker post it is

[Metalshaper]

They are also called "Lantern toolposts" or Lantern and rocker toolposts..
do a google image search and you will see.. I learned em' as Lantern??

Respect Always
Metalshaper/Jonathan

[kudu]

I think your plan is viable . Coming from a Journeyman Machinist.   You don't have to hit any dimensions right on if its all CUSTOM .750 could be .777 - .801 whatever you want. BUT I would keep the breech for 9" or there about as previously said