Internal shape of Ferguson barreled breech?

[Naphtali]

I have a new Ferguson barreled breech with .52-caliber barrel. I am considering replacing that barrel with a barrel of larger bore size - somewhere between .65- and .69-caliber.

Loading its RB consists of dropping it into the vertical breech bolt's loading port, then tilting rifle downward slightly at the muzzle to cause RB to roll to front of chamber. What is the shape of this "front of chamber?"

Is transition from chamber to barrel proper as a straight taper, or a slight lip or flange, or nothing at all, or something I haven't thought of? And if there is a step or lip or flange or other definite transition, does it change [proportionally??] as bore size changes?

[mjm46@bellsouth.net]

Here is a link to some patent drawings, it looks like it's showing a chamber before the rifling starts.

http://www.google.com/imgres?imgurl=http://www.11thpa.org/news/mbo51-1d.gif&imgrefurl=http://www.11thpa.org/ferguson.html&h=983&w=1038&sz=32&tbnid=J4AZ__ov8Ug0GM:&tbnh=83&tbnw=88&zoom=1&usg=__gJ1vwyU6QPNf69kNfauWtMahLCQ=&docid=ZEbyyFQ85vMlQM&hl=en&sa=X&ei=qutaUbKIL4e49QTlkYHIDw&sqi=2&ved=0CEMQ9QEwBA&dur=910

Here is another with a little more detail;

http://www.11thpa.org/news/mbo51-1c.gif

[JTR]

Maybe just unscrew the breech/loading gate gizmo, then drop a long thin mirror down in there and take a look...

John

[Acer Saccharum]

You can make a 'cerro-safe' casting of the original chamber and comparatively machine the new barrel.

[4ster]

Can you stick your finger in and feel the transition?  Although not a micrometer it might give you enough information to figure out the relationship between the chamber and the rifling.  I'll try it with mine today.

[TMerkley]

The only trasition I believe would be the beginning of the rifling itself that would prevent the ball from rolling out.  How is the barrel attacted to the breech?  Is the breech chamer machined into the barrel and then attached to the reciever like that of a modern firearm?

[Naphtali]

The barrel is threaded into breech. And nearly every responder is correct - I'm putting the cart before the horse. When I have the replacement barrel [blank??], we can cerrosafe the OEM's chamber.

I'm placing WANTED advertisement to try to speed the process.

[Jerry V Lape]

I am just posing some questions? The chamber has to be large enough in diameter to get the heavily lubed ball to load with gravity alone doesn't it?  And then it would need rifling tight enough to have the upset of the ball seal the bore without a patch yet minor enough not to appear as a bore obstruction - is that a correct assumption?  The chamber behind the ball would need adequate volume to contain the service charge of powder without significant voids so the total chamber would need to be the sum of the ball and powder volume.  Are those known quantities?  

I bet Ferguson did a lot of experimenting with ball size, chamber dimensions and bore dimensions to get it right.  Hope you can get a good cerro safe measurement to find out what Ferguson found to be useful.  I would think the chamber size to bore transition is going to be the critical factor and will probably look something like a small muzzle crown or possibly like a coned muzzle.  The drawings seem to show two options for this transition.  One is a little rim as a crown, the other looks cone shaped.   Hope you will post your findings as I think they would be very informative.  

[Acer Saccharum]

Thinking out loud:

I would expect that the chamber is bigger than the Bore  + rifling diameterss. I would also think there would be a forcing cone leading up to the rifling, much as in a revolver barrel or BP cartridge chamber. Ball size should be as large or slightly larger than rifling diam, and chamber big enuff for ball to drop into.

You might want to work up some loads in a similar sized muzzle loader, then mock up some chambers so you can see where the powder level is on it. That will give you a rough length of chamber.

Unfortunately, once you're done making up your barre and chamber, that's the load you're stuck with. So you want to do as much homework as possible.

Oh, if your chamber is too long, you could unscrew it, and set it back a thread or two. If your chamber is not long enuff, like you want more horsepower, take it out and ream the chamber deeper.

[Jerry V Lape]

Acer,  wouldn't it be possible to have a large chamber and limit powder by using a wad behind the ball?  This would give a little flexibility with respect to varying the load once the chamber is cut? 

[4ster]

I tried to stick my pinky into the chamber to try to get the "feel" of how the chamber/rifling area is shaped.  My pinky isn't long enough.  So I made a little inspection mirror to look into the chamber and was able to get a clear view. 

The following applies to a Rifle Shoppe version of the Ferguson:
The chamber is larger than the bore, there is a shoulder to the groove depth of the bore and and the rifling starts immediately at the shoulder also.

I made a sketch to make my verbiage clearer.

[Acer Saccharum]

If there is a sharp shoulder betwixt chamber and rifling, there will be a little ring of lead left behind with every shot. It's got to have a tapered forcing cone.

[mjm46@bellsouth.net]

If there is a sharp shoulder betwixt chamber and rifling, there will be a little ring of lead left behind with every shot. It's got to have a tapered forcing cone.

That's what I was thinking. Kind of what you have in a modern shot gun.

[4ster]

I'll look again, maybe I wasn't seeing right.

[Acer Saccharum]

Take a little wad of Silly Putty, wrap it around a stick or wire, and press it against the side of the chamber. You can get a crystal clear impression of the detail.

[D. Taylor Sapergia]

In the Ferguson rifle I made those many years ago, there was room for a lubed .650" ball and ~65 gr. FFg GOEX.  I found that fouling in the chamber affected the way the ball would/wouldn't roll up to the end, and thus affected how much powder I could introduce.  So I made a little "L" shap0ed brass starter that levered the ball tightly against the end of the chamber, so uniform charges could be used.  It shot nicely and was lots of fun.

[4ster]

After a second look I stand by the drawing above.  There *may* be a slight chamfering on the the top of the rifling but it isn't much.  I also pressed a ball into the chamber with my version of Taylor's starter then pushed the ball out again with the ram rod.  The rifling marks looked like there was little or no chamfer at the start of the rifling.  

Off topic here a little but Taylor mentioned ball diameter.  I subscribe to the theory that the Ferguson fired a ball significantly smaller that the bore of the gun.  So while a .65 ball will roll down a clean loading chamber, I shoot a .615 ball which just engages the rifling but not fill the bore to the base of the grooves.  A ball sent down the bore just shows the imprint of the rifling only.  I don't think .65 is what was used historically, hence the fouling problems reported with this system when modern shooters  tried to use this size ball.  Historical records note the requisitioning of carbine ball (.615 at the time) for the Ferguson, and Ferguson himself wrote that his design required that the ball be smaller than the bore.

[Acer Saccharum]

Just thinking out loud:

A small ball might not provide enough resistance, therefore, poor combustion and more fouling. A small ball might not upset to completely fill the bore and grooves. Gas cutting, fouling and leading are all possible if the ball doesn't fill the bore completely.

Also, this Ferguson rifle was developed way before cartridge arms were invented. There wasn't a proven design path for Ferguson to follow. So just because he built it that way, doesn't mean that it was perfect or the best way to chamber a breech loader.

[Bill Paton]

Read "Every Insult and Indignity", available in this site's classifieds under "Books". Author has experimented with Ferguson's rifle and (in my mind) has answered many of these questions. He says an undersized ball is important to keep the bbl clean (he thinks the blow-by cleans out fouling), and with it plus the correct lube and powder he can shoot 62 rounds without cleaning. I can't do that with a Kentucky  or musket, both of which the Ferguson was up against.  And he has put thousands of rounds through the barrel without wearing out the rifling, inspite of the blow-by. This book is a "must read" for anybody interested in Ferguson or his rifle. It covers this thread very well and more.

[D. Taylor Sapergia]

When I built the Ferguson, I knew nothing about it's loading or shooting, except what I had read about Ferguson himself, and the performances he gave to sell his product.
I asked Jesse Melotte at TRS and it was he who said the rifle, with a .65 cal barrel, needed the .650 ball.  Ray Rapine, who made my mold concurred.  It was the fouling in the drop-breech threads that limited how many shots could be fired - not fouling in the bore.
And if you cannot shoot more than 62 rounds from a longrifle without having to clean, you are not using a suitable patch/lube/ball combination....IMHO!!

[4ster]

I got the same info from Jesse Melotte when I bought mine and purchased a mold from Ray also.  I think it was .648.  I sold that mold because I thought it was too big.  I think Jesse and Ray thought that the ball should be about bore size because that is the conventional, modern day, wisdom. 

I've not had problems with fouling shooting mine.  The breech screw will start binding, depending on weather conditions and how well I lubed it when I put it away after the last shooting session but that is fixed with a little water or spit on the threads.  Balls always go in easy and the powder charge stays the same shot to shot.  No fouling or leading issues at all at the end of any shooting session.  The gun will be dirty but will still function fine.

TRS reproduction Fergusons got a reputation for becoming inoperable after a few shots, from my reading that is from shooting .65 ball and not lubing the ball and the breech screw.  But there are a lot of ways to skin a cat, I'm sure.  I just started shooting with a smaller ball since that seemed to be what was done historically and the larger ball seemed to be contributing to the fouling problem.

[Acer Saccharum]

Thanks for the info, gents.

Tom