Coning tool

[necchi]

just someone who takes a set of calipers and a notebook with him to gun shows. This is apparently unusual.

It is?
They bring smart phones with cameras, with the internet at hand too.
All that makes it very easy to document observations, price check, verify random claims by the seller and other data.

 

[Artificer]

Hi Elnathan,

Thank you for providing the pictures and information.

If the “round coning” on the original rifles is concentric and between 3/8” and ½” deep, then I don’t see how that could have been done by hand filing alone and would have required reaming. Actually, I would expect such reaming would be done while the barrel was still smooth and before rifling was accomplished. That way the rifling cutter at the deepest depth (at least .010” to between .012” to .014” deep) would make a faint impression of rifling near the coned muzzle and that would give a guide to hand filing the groove to full depth near the muzzle. Of course this is assuming something that should be asked to confirm whether it is true. Are the depth of the grooves equally deep throughout the coned area of the bore and equal to the depth in the “non coned” section of the bore?

BTW, I appreciate you providing the pictures. The second picture is somewhat similar to an 18th century muzzle I have seen here or an the ALR forum.

There is another kind of original muzzle treatment that may be described as “relieving the muzzle,” though some may call it “coning.” It is when a flat file is used to file the lands away between the grooves ”“ giving a hexagon shape to the muzzle between the grooves. I mention this only because it would not require reaming and would not be concentric.

Gus

 

[M. De Land]

I can't imagine going to the trouble of making potentially 500 trips down a rifle bore single point cutting all grooves to final depth then screwing the hole works up with a file in the muzzle.
I believe cone reaming with a close fitting pilot is the most accurate method as a lathe cut depends on close to zero run out to get a concentric cone and all bores have at least some run out of co-axis.
A close fitting piloted reamer in a tail stock of a lathe with a floating reamer chuck will allow the reamer to move with the bore run out keeping the reamer co-axial.
This is the most accurate way to cut modern chambers as well which is precisely the same principle used.

 

[Black Hand]

And therein lies the issue - It isn't so much what WE would have done, rather what THEY actually did...

 

[M. De Land]

They probably filed and lapped level with the groove bottoms at the muzzle for a depth and concentric gauge as reamers were hard to make.
Cone making is partial taper cutting of the lands not the grooves in all that I have seen.

 

[Elnathan]

Hi Elnathan,
If the “round coning” on the original rifles is concentric and between 3/8” and ½” deep, then I don’t see how that could have been done by hand filing alone and would have required reaming. Actually, I would expect such reaming would be done while the barrel was still smooth and before rifling was accomplished. That way the rifling cutter at the deepest depth (at least .010” to between .012” to .014” deep) would make a faint impression of rifling near the coned muzzle and that would give a guide to hand filing the groove to full depth near the muzzle. Of course this is assuming something that should be asked to confirm whether it is true. Are the depth of the grooves equally deep throughout the coned area of the bore and equal to the depth in the “non coned” section of the bore?

Gus, I've been operating as much by feel as by sight. It is immensely difficult to get an accurate reading between lands with a seven-grooved barrel - you wouldn't think it would be all that difficult, but it really is. I now realize why two people can measure the same rifle and get two very different bore measurements. To get the information you are asking for would require making a casting of the muzzle and measuring that, I suspect. The best I can say right now is that the rifling at the muzzle looks at least as deep as I'd expect to see inside the bore.

They may really have reamed it out prior to rifling. That would aid in getting the cutters started if they were rifling from the muzzle. As the barrel wore and was freshed out, though, that original cone would have disappeared.

There is another kind of original muzzle treatment that may be described as “relieving the muzzle,” though some may call it “coning.” It is when a flat file is used to file the lands away between the grooves ”“ giving a hexagon shape to the muzzle between the grooves. I mention this only because it would not require reaming and would not be concentric.

I've seen pictures of that, too. I haven't had a chance to measure one myself, but "Longknife" (Ed Hamburg) has measured and reported that some of those are coned as well. I can't post a link, but if you look for "Barrel Coning Distilled" on ALR you should be able to find his post.


I really need to come up with a set of tools that will allow me to measure down the barrel a bit better.

 

[Artificer]

Hi M.D.,

It is such a shame we lost Gary Brumfield (Past Master at the Colonial Williamsburg Gun Shop) to cancer a few years ago, because I think we would all learn a lot as to how he would have answered how they might have done it.

At risk of repeating myself, I would think a period gunsmith would have reamed the cone shape near the muzzle, after reaming the bore and before rifling the barrel. That would have made the most concentric cone possible near the muzzle. Further, since the rifling was normally at least .010" deep and often .012" to .014" deep, that would mean when the barrel was rifled, the very bottom of the rifling would have come close to the muzzle, even after it was reamed in a concentric cone. That would have saved A WHOLE BUNCH of hand filing and of course the bottom of the rifling near the muzzle would have been a much surer and easier guide to deepen the grooves by hand filing at the muzzle.

In the following link on Gary Brumfield's old site, it shows how they used a square reamer to finish ream the bore smooth before rifling. Before his passing, Gary had mentioned that they could normally hold a tolerance of between .001" to .002" throughout the bore and no more than .003" larger in the bore and especially at the breech - where reaming was always started.

A shorter tapered square reamer could easily have made a fairly concentric cone (and MUCH MORE concentric than possible by hand filing), when used in conjunction with a "sliver of wood as a guide" similar to the reamer photo image above the caption, "Two views of the square reamer and its wooden backing strip. Only the two corners opposite the hickory strip cut. As Wallace said in the Gunsmith of Williamsburg film, "the borings are as fine as face powder." http://flintriflesmith.com/ToolsandTechniques/barrel_making.htm

Now of course this is only informed speculation or a S.W.A.G. at best on how they could have done it, but it is a way they could have done it with the technology readily available even in remote one or two man gun shops.

Gus

 

[Artificer]

Of course, the shorter tapered reamer would have been started at the muzzle, instead of at the breech.

Sorry, should have mentioned that in my post above.

Gus

 

[Elnathan]

M.D.,

One guy here, Herb, has filed out the lands of a couple rifles to exactly replicate some original Hawkens, I believe.

Incidentally, that is his picture of the Bridger Hawken I borrowed up above, and I just found the reference to it being coned approximately 1/4" back.

 

[Artificer]

Incidentally, that is his picture of the Bridger Hawken I borrowed up above, and I just found the reference to it being coned approximately 1/4" back.

Please don't take this as personal criticism, but hand filing a cone only 1/4" back from the muzzle would have been significantly easier to do and keep concentric than going back 3/8" to 1/2" for cone. Going that much further back and keeping it concentric would have required a reamer in my estimation.

Gus

 

[Elnathan]

Incidentally, that is his picture of the Bridger Hawken I borrowed up above, and I just found the reference to it being coned approximately 1/4" back.

Please don't take this as personal criticism, but hand filing a cone only 1/4" back from the muzzle would have been significantly easier to do and keep concentric than going back 3/8" to 1/2" for cone. Going that much further back and keeping it concentric would have required a reamer in my estimation.

Gus

Well, I went back and double checked my notes, and the only length I wrote down was one instance of 3/8," so perhaps I should have written 1/4" to 3/8." Upon reflection i think that that is a more accurate figure of what I was seeing, and is actually kind of what I thought I wrote... :redface:

It is possible, you know, that they originally filed it out, and then it wore right at the junction between cone and bore. That would give the appearance/feel of a longer cone.

I have to say, though, that Mark Elliot, who puts rods down muzzles as a regular thing while photographing guns professionally, says over on ALR that he sees a lot of cones in the .5-1.5" length. My calipers don't reach that far, so maybe I'm missing something.

BTW, has it occurred to anyone else that, if coning is common among old rifles, most of the published data overestimates surviving rifle calibers? That goes some way towards reconciling period accounts of rifle bores with surviving averages today. :hmm:

 

[Artificer]

Well, I went back and double checked my notes, and the only length I wrote down was one instance of 3/8," so perhaps I should have written 1/4" to 3/8." Upon reflection i think that that is a more accurate figure of what I was seeing, and is actually kind of what I thought I wrote... :redface::

OK, thanks for the better explanation.

It is possible, you know, that they originally filed it out, and then it wore right at the junction between cone and bore. That would give the appearance/feel of a longer cone.

This is VERY possible because wood ramrods will pick up dirt, sand, and other contaminants that wind up getting on and/or embedded in the ramrods and thus turn them into a “lap” inside the bore.

I have to say, though, that Mark Elliot, who puts rods down muzzles as a regular thing while photographing guns professionally, says over on ALR that he sees a lot of cones in the .5-1.5" length. My calipers don't reach that far, so maybe I'm missing something.

Did Mark say it was coned that far back or was the bore tapered that far back? There is no doubt in my mind that a cone depth of 1-1.5” would have to have been done by a reamer, if it was done when the barrel was first made.

BTW, has it occurred to anyone else that, if coning is common among old rifles, most of the published data overestimates surviving rifle calibers? That goes some way towards reconciling period accounts of rifle bores with surviving averages today. :hmm:

That’s possible, but it depends a lot on who was using the dial calipers to check the bore size. Just as an example I’m very familiar with, many people who do not have a machinist background, can’t get an accurate reading of the bore diameter on Minie’ Ball rifling, even though they are using Precision Dial or Precision Digital Caliper. (Maybe I’m far too set in my ways, but I cannot get many Digital Calipers to come anywhere close to the accuracy I get with a Precision Dial Caliper.) Worse still are those who depend solely on the Triangular Shaped Brass or Steel “Pocket Bore Gages.” Have to admit I always keep one of those in my pocket when going to gun shows, but it is only for a very rough “comparable” measurement and not for a precision measurement.

Gus

 

[Rifleman1776]

M.D.,

One guy here, Herb, has filed out the lands of a couple rifles to exactly replicate some original Hawkens, I believe.

Incidentally, that is his picture of the Bridger Hawken I borrowed up above, and I just found the reference to it being coned approximately 1/4" back.

Yes, but that is Herb. There are few others with his skills.

 

[M. De Land]

Gus, a four sided reamer as used in reaming a drilled and straightened barrel, would not work well in tapering a cone as the lands would not be a good bearing opposite the two cutting edges. It most certainly would induce chatter. Probably a ball mold cherry would be a good starter for a barrel cone then a half taper reamer with one cutting face. I have cut several full cartridge chambers with tapered half reamers made right here in my shop. They cut slow but they cut surprisingly smoothly.
You'd need some kind of bore diameter pilot and carefully feel the bore center as is done when tapping a threaded hole, if done from the muzzle.
The very best way to cut a cone with a reamer would be to pull the breech plug, make two brass slip fit bearing bushings( one in the breech and one in the muzzle) and full length driving rod. The reamer is pulled and driven from the front end following the pilot into the bore. This is how shot guns are back bored and how pistol barrels are crowned and breech chamfered to maintain co-axis.

 

[Artificer]

Gus, a four sided reamer as used in reaming a drilled and straightened barrel, would not work well in tapering a cone as the lands would not be a good bearing opposite the two cutting edges. It most certainly would induce chatter.

M.D.

There would be no lands to introduce chatter when a barrel was finish reamed, then reamed for the cone in front and then rifled; as I mentioned earlier. That is why the cone reaming would have been done before rifling.

Gus

 

[Artificer]

M.D.

Maybe I was too brief in my reply above. If you look at the link I provided earlier, the period square reamer was inlet/set into a wood partial dowel so that only two edges of the reamer made contact/scraped the barrel wall in the barrel.

"Two views of the square reamer and its wooden backing strip. Only the two corners opposite the hickory strip cut. As Wallace said in the Gunsmith of Williamsburg film, "the borings are as fine as face powder."
http://flintriflesmith.com/ToolsandTechniques/barrel_making.htm

Therefore, the square reamer in the wooden strip is effectively turned into a Half Reamer because only two corners of the square reamer would be cutting/reaming the bore.

Hope this is easier to understand than my post immediately above.

Gus

 

[M. De Land]

Well the trouble with that method is you do not want to change the reamed bore diameter at any point breech to muzzle when single point scrape or hook cutting grooves as the depth of groove will change and be shallow both at entry and exit even if the reamed bore is perfectly level.
The reason of course is the cutting teeth are not fully supported fore and aft at entry and exit.
This can work to good effect at the muzzle as choke is induced in the groove bottom but not at the land top.
The squared muzzle with a piloted reamer drawn from the breech would maintain perfect bore co- axis and if the pilot is a snug slip fit no chatter would be induced.
A reamer chatter is a dreadful thing to have occur and is almost impossible to totally correct out side of a long lapping operation. They are almost always induced by a small pilot diameter, no pilot reaming or reamer flute equal-distant placement.

 

[Artificer]

Hi M.D.

Yes I understand, but I suspect you and I think more like machinists, while in the original period - many/most gunsmiths thought more like Blacksmiths.

IOW, I speculate that small Rifle Shops in the American Colonies would have used a tapered square reamer with a wood backing/support and with a wood extension ahead of the reamer, that would also act as a pilot to keep the reamer concentric. This would be entered from the muzzle to ream a "relief" or "cone." This is something that would be simple enough and well within their technological capabilities.

While Diderot shows piloted reamers in the period, I think those reamers would have been uncommon to possibly nonexistent in small American Rifle Shops. Piloted Reamers were probably only used in the "production" specialty shops in England or the Continent, due to their cost - even if the cost was only materials/labor.

However, this is all pure speculation, though based on the technological abilities of the period.

Gus

 

[George]

I've never come across any reference which could be considered a description of coning as we think of it, today. What I have seen several mentions of is the increase in bore size at breech and muzzle which was apparently fairly commonly done early on, say before mid-18th century. This was on smoothbore guns, not rifles, and was done at the time of manufacture, not after-market. It was called "bell mouth" by Cleator in 1790, describing Spanish barrels, but he doesn't say how much of an increase there was in bore diameter at the muzzle.

I have an 18th-century smoothbore barrel which has that bell mouth. It expands from 28 gauge/.56 caliber to 20 gauge/.61 caliber.

Just curious, is there any period description of coning of a rifle? Did anybody ever write it down?

Spence

 

[Black Hand]

Just curious, is there any period description of coning of a rifle? Did anybody ever write it down?

Spence

Spence,
I have asked this very question for each coning discussion in which I have been involved and nothing has yet been provided.