Tapering Straight Barrels - per Dunlap

Clemson

New member
The recent thread on turning down an existing barrel got me to remembering (a sometime thing nowadays) a letter that I got a few years ago when I sent an inquiry to the American Rifleman magazine's "Dope Bag."

I got back a letter from none other than Roy Dunlap. Check out the little drawing in the corner giving me his method.

I keep this letter as a bookmark in my copy of Dunlap's Gunsmithing.

Clemson

BarrelFitting.jpg
 
Friend Clemson

Friend Clemson:

My friend, would you do Bill Calfee a favor, please?

I have an article coming up in Precision Shooting, I think, that the letter you posted will become so profound about........

The way your letter describes how to fit a rifle barrel, for accuracy, has an extremely great bearing on my article........

Please, friend Clemson, if you don't subscribe to Precision Shooting Magazine, please get hold of a copy after the article is published....it will become obvious what your letter means to that article...

The Article will be titled "Potpourri No. 4"

Thank you my friend!

Your friend. Bill Calfee Thank you again!
 
Friend Clemson

Friend Clemson:

I had to post again as your letter from Roy Dunlap will be so important to my Potpourri #4 article in Precision Shooting....here's why:

I quote from the letter by Roy Dunlap:

" Thread until you can screw on the barrel 3/4 way by hand, making sure you have relief at the shank-shoulder area for receiver, so barrel can go all the way to shoulder when receiver wrench is used."

Friend Clemson: Please read my article when it comes out........borrow it if you don't subscribe...you will see that what Roy wrote in his letter about barrel fitting, influenced a bunch of folks, including me.......But, not exactly like you might think...............

Friend Clemson, when the article is published, I want to say more...

Your friend, Bill Calfe
 
?????? Ditto

If Mr. Dunlap is chucked on the tenon with a 3-jaw as he states, then uses a floating center in the muzzle end to turn the taper?? Did I read this correctly??

Then he threads the tenon till it screws on 3/4 of the way??? Did I misunderstand something here??

Could someone in the know please explain at least these two operations..
 
May I refer you to the article in the book Gunsmithing Tips & Projects by ROY DUNLAP pages 272 through 276. Wolf Publishing. I think the article will shed much light on the why the late ROY DUNLAP did what he wrote in the Dope Bag letter.

Right after that article, the late NEAL KNOX had another great article that is worth reading on chambering.
 
Two different things going on me'thinks ;)

The offset is accomplished by using the three-jaw lightly clamped to a (hand-filed?) "lump" or oversized egg on the shank.......In other words the shank is left over sized and a pivot area is made JUST for turning the taper, then you straighten 'er out, cut a chucking parallel on the muzzle and "thread so tightly that you can only turn it on 3/4 way without a wrench".


Then you wrench 'er tight............sCARY!! with todays SS actions/bbls!


At least that's what I see.


al
 
Jackie,
A lot of these old timers (as opposed to us who are still young and fresh) were very economical with words and apparently assumed the reader had some clairvoyant abilities.
Roy Dunlap first describes tapering the barrel by holding it in the three jaw chuck then offsetting the tailstock to cut the taper. As a machinist, you are likely puzzled because you know this wouldn't work very well. By offsetting the tailstock you are essentially bending the barrel to try and cut a taper. Such a setup just doesn't make sense just shows he didn't want to take the trouble to set up the driving plate and centers.
He then, without the benefit of puncuation, describes turning a short piece at the muzzle to hold in the chuck to thread on the tailstock center. One assumes the tailstock center is re-aligned prior to turning the short section to hold in the chuck.
I can't say for sure but it's entirely possible I've tapered nearly as many barrels as Roy Dunlap did and I wouldn't even try that method.
As far as the threading and chambering while holding in the three jaw chuck goes, no modern BR gunsmith would admit to doing such a thing even if he did so!
Still, a fascinating look at the way things used to be done. Those books by Roy Dunlap, Wayne Vickery, and, especially, the two volumes by James Howe are an amazing storehouse of arcane knowledge. Regards, Bill.
 
My third grade "edumication" does not allow me to read things not written in to the letter that was posted (just not smart enough, I guess).

Where in that letter does it talk about off setting the tail stock?

Where in that letter does it talk about cutting a taper?

The letter as (my poor book learnin) reads to me about turning a barrel.

I salute all that are able to find so much more than what is written in that letter!

The part that is of interest is the section that reads about why he only does the 3/4 threading into the receiver. If you read the article that I referenced you will understand why this was so important to Mr. DUNLAP. He tells the reader it's because of the threads in the receiver are sometimes tapered towards the bottom of the receiver ring.

A great article is also in the above mentioned book on chambering by Bob Brackney. Worth the time to read over and over again.

Maybe the "Old timers" were so economical with words, because they knew how to answer the question asked of them?
 
Floating center = Live center ?
Shank = Tennon ?

It seems pretty straight forward, with the exception of 2 things.

1. What a floating center is. and 2. How the breech is stabilized for the threading/chambering operation.

Reading between the lines, the three jaw chuck is clamped on the muzzle, which 1" of has no taper.

It doesn't say it, but the tennon is threaded in a steady rest or on the dead center?

This process seems very crude compared to other procedures I've been researching. Thanks for the info, but I do not plan to follow this.
 
Bill Calfee: I will certainly try to get a copy of your article. Which month of Precision Shooting do you expect to see it in? I don't subscribe, but I will try to look it up.

Others: What you are missing is the letter that I sent to the Dope Bag. Unfortunately, I don't have it either. As I recall, I was wanting to make a barrel for an L461 Sako action. There were no commercial tapers that would work for the little gun, so I wanted to start with a blank. I asked, as I recall, if I could do the taper by offsetting the tailstock, and whether it was better to cut toward the breech or toward the muzzle.

I enjoy reading this forum even though I am not a benchrest shooter (or smith). I make primarily hunting rifles, and I chamber in the (shudder) steady rest. At the time Mr. Dunlap wrote his book, I doubt that many gunsmiths had access to the kinds of equipment that we see today. I can recall a lot of Atlas lathes in garages turning out barrel work on Mausers. Many of those fellows didn't even have a 4-jaw chuck.

I never actually tried the method that Mr. Dunlap suggested, turning a "ring" on the tennon and letting it "float" in the three-jaw chuck, presumably driven by a dog. I have no doubt that it could be done that way, however. Nowadays I have a 13x40 lathe with a taper attachment, and if I need to reduce the size of a barrel, I set it up between centers, or occasionally in a 5C collet, and turn it down using that taper attachment. Once I finally got that tailstock dialed in, I didn't want to mess with offsetting it!

The letter is a piece of nostalgia, and I enjoy looking at it whenever I refer to the book, which is pretty darned often, come to think of it.........

Clemson:)
 
Friend Clemson

Friend Clemson:

I do not have conformation that the article will actually be published....

If it is published I usually get conformation by the middle of the month...

The article is as crummy written as are most of my articles but it involves a detailed experiment I ran to determine the requirements necessary to make a threaded, barrel/action system, produce accuracy.

The results of the experiment even surprised me.........

When, and if, you get to read the article it will become obvious how the letter of yours, from Roy Dunlap, comes into play.....

Your friend, Bill Calfee
 
Dunlap Quality

I saw one of his Rem 37's in a beautiful hand crafted RH Thumb hole stock. I believe the wood is Walnut. I believe the guy is really thinking about selling it. Shame it's for a righty.
 
My third grade "edumication" does not allow me to read things not written in to the letter that was posted (just not smart enough, I guess).

Where in that letter does it talk about off setting the tail stock?

Where in that letter does it talk about cutting a taper?

The letter as (my poor book learnin) reads to me about turning a barrel.

I salute all that are able to find so much more than what is written in that letter!

The part that is of interest is the section that reads about why he only does the 3/4 threading into the receiver. If you read the article that I referenced you will understand why this was so important to Mr. DUNLAP. He tells the reader it's because of the threads in the receiver are sometimes tapered towards the bottom of the receiver ring.

A great article is also in the above mentioned book on chambering by Bob Brackney. Worth the time to read over and over again.

Maybe the "Old timers" were so economical with words, because they knew how to answer the question asked of them?
Big Al,
It was the rather cryptic phrase "can use offset to turn taper OK" that led me to believe he meant to "use offset to turn taper". I've gone back and re-read this several times and it still seems to me to refer to the cutting of a taper. Add to this the handwritten note about the special shaping of the shank to allow the cutting of a sharper taper and you can see how I might have been fooled into thinking he was talking about tapering a barrel as well as threading.
Since you see no reference to the cutting of a taper in either of these cases, perhaps you can tell me what the word "taper" meant back then. If I recall correctly, if I discussed turning a taper with a customer back in 1991, we both understood it to mean I intended to taper the barrel by turning it in the lathe; frequently by utilizing an "offset" at the tailstock. If I've been misusing the term all these years, I apologize to those I may have confused by so doing. Regards, Bill.
 
Not to mention the point that the handwritten note in the bottom left corner reads "To turn a SHARP TAPER on barrels cut shank oversize a little and shaped so (cross section)" and then "chuck jaws on ring allow barrel to move in turning"

(caps mine ;) )


He then draws in the upper chuck jaw but doesn't leave room to draw the others.


al
 
Can we then agree, that he makes no mention of offsetting the tail stock?
 
We can agree he does not use the phrase, "offset the tailstock". He does, however, use the phrase "use floating center on tailstock at muzzle". This phrase is immediately followed by "can use offset to cut taper OK". Offset of what, pray tell? Any machinist would reckon that to refer to offsetting the tailstock center to cut a taper; especially considering the mention of the tailstock immediately previous. I suppose he could be referring to tool offset but just where that would come in to cutting a taper, I'm not sure. Regards, Bill
 
The O/S spherical ring in the sketch is intended to act as a sort of "universal joint" to allow the barrel to "squirm" in the chuck jaws a little while turning the taper with the tailstock offset.

There really isn't anything wrong with offseting the tailstock to turn a taper, nor is it difficult to set it or return it to the center. The biggest problem is keeping chatter under control. a sharp-pointed hand-ground tool with exaggerated back-rake and side-rake angles (angles on top of the tool) along with a high enough rate of feed to "peel" the stock from the work gives the best results.

Here are a few formulas that you can use to get the set-up right:

Taper per inch:
.......................(D-d)
....................._______

.................length of taper




Tailstock offset:

....................OL............(D-d)
...................____...X....______

....................TL...............2

(please excuse the periods...or blame the software)


D= Major dia.
d= Minor dia.
OL= Overall length
TL= Taper length

-Dave-:)
 
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