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| | |-+  recontouring already finnished barrels
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Author Topic: recontouring already finnished barrels  (Read 2319 times)
smylee grouch
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« on: February 26, 2010, 10:53:11 PM »

I have a couple of heavey weight (1 1/8 " dia.) 50 cal. barrels that i would like to have straight tappered, 1 1/8 to 1 in.   If i did this, would the accuracy of the barrels suffer?         Gary Trapper
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Pete G.
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« Reply #1 on: February 27, 2010, 10:10:35 AM »

I don't know if there is any way to predict that. There is no way to determine what, if any internal stress exists. Some folks swear by cryogenically treated barrels to relieve internal stresses, others view it in the relm of witchcraft. Probably the true story is somewhere between. Depends on the barrel.

If they were my barrels I would contour them to my liking and see what happens.
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Acer Saccharum
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« Reply #2 on: February 27, 2010, 10:15:40 AM »

Just some things to watch for:

This  can be such a complex issue. If the barrel is stressed from button rifling, or stress from milling, or turning exist in the barrel, this can cause the barrel to curve once you remove some of the outer layer of metal.

If the barrel has been stress relieved, you might not encounter any problems at all.

Every barrel I have turned, I've had to straighten in between passes.

Tom
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The other DWS
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« Reply #3 on: February 27, 2010, 10:19:07 AM »

I'm not a machinist or a gunsmith, but I stay at a lot of Holiday Inns------

I know a couple really good machinist/gunsmiths, custom gunbuilders guild guys, friends who have done work for me building single shots.  the question of reshaping octagonal barrels has come up since I've had it done on single shots I use in ASSRA competition.

A lot depends on how the original barrel was handled,  the steel bar has manufacturing stresses that have to be relieved, each step of machining, exterior as well as drilling, rifling, and reaming can add more as the bar is turned into a gun barrel. experienced  gunsmiths know all about this and know how to normalize the stresses that can cause a barrel to warp.  

Heat from firing can cause a barrels inherent stresses to become active shifting impact point. ( this may not be too big an issue with our muzzle loading BP rifles) thats why most precision target rifles have short fat very stiff barrels.  Barrel vibration harmonics are another factor and I have no idea how having a long barrel pinned in several location affects this.

I suspect that planing down an octagonal barrel from straight to taper,  might create or reactivate normalized stresses if not done properly.  It seems to me there must be a process to avoid creating them, or normalizing them afterwards.
 I think if I were considering doing so myself I PM someone like Don Getz or contact one of the good custom barrel makers like Rice, Colraine, or others and ask their advice before proceeding any farther.
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Don Getz
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« Reply #4 on: February 27, 2010, 10:25:23 AM »

I'm not quite sure how you are going to go about doing this taper?   Do you have a milling machine?   If you are planning
to file it down, you will be delaying your gun building for a while.....it will take one heck of a lot of filing, and will be difficult
to keep it uniform.   Even if you are going to mill it down, when you remove the steel from one flat, it will create a lot of
heat and will, most likely, warp.  You would then have to straighten it and do the opposite flat, then repeat the whole
process again.   If I were you, I would try to sell it and take the money and apply it toward the purchase of a new straight tapered or swamped barrel.................Don
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Bill D
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« Reply #5 on: February 27, 2010, 11:05:16 AM »

Not trying to steal this thread, but while we're on the subject......  What stresses are involved in turning a octagon barrel round?

Bill
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Acer Saccharum
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« Reply #6 on: February 27, 2010, 11:45:49 AM »

hex barrel?

Never saw one with six sides. You must mean eight.

Is it normalized? Milled flats, or is it a drawn octagon product, like Dixie used to sell?


I seldom agree with Donnie Getz, but you'd be better off selling what you have and buying what you need.

A friend wrote me with some historical corrections to my post:

Barrel forging was not done at a mill. If water power was involved, by using a trip hammer, the place would be a "forge" not a "mill." Some 19th century military barrels made by punching a short tube and rolling it out longer but that doen't apply to any longrifle barrels I know of.

Barrel boring was sometimes done in mills and many were water powered but a few were actually horse powered --horse in basement of shop turning a shaft sort of like a pug mill.

Rifling needed no water or horse power and therefore wasn't "located down the mill stream."
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Bill D
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« Reply #7 on: February 27, 2010, 12:09:42 PM »

Hi Tom,  I fixed it, octagon.    Just wondering.   Straight barrels are easy to get, O/R are not.   

Bill
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Acer Saccharum
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« Reply #8 on: February 27, 2010, 12:28:10 PM »

I think you can end up with junk pretty quickly. I have gotten lucky a few times, but be prepared to throw the barrel away before you get started. I am not saying don't try it. I am just saying that the chance are pretty good you'll end up with something less than satisfactory unless you have a well equipped shop with barrel straightening abilities and a bunch of experience under your belt. But you CAN get lucky, and if it is what you really want to try, you should do it.

I have ruined a few, and turned a few usable ones, but I don't really know what I'm doing.

Tom
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Dave B
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« Reply #9 on: February 27, 2010, 01:20:42 PM »

You need to ask your self if the effort of doing all that work and your time is worth it. You may find selling them and buying a barrel ready made more cost effective. I am not a target shooter but I have been told by those who are that the more consistent the bore the better the accuracy. If a barrel of tapered thickness is compared to uniform thinckness you are going to find the uniform is going to be more accurate. I dont know if the heat build up on a barrel will be the same for a tapered vs uniform but a colder section from a thinner barrel will make the bore inconsistent. I know this is nit picking but I got this from a barrel maker take it for what its worth.
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Dave Blaisdell
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« Reply #10 on: February 27, 2010, 02:17:39 PM »

one reason "uniform thickness" barrels are "more accurate" than tapered ones is simply due to greater stiffness and resistant to harmonic vibrations and well as greater weight for shooter steadiness---hence  the "bull barrels" found on modern target arms.

one had to take into consideration the difference between rifle--or barrel-accuracy and shooter-with-rifle-accuracy.

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g.pennell
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« Reply #11 on: February 27, 2010, 04:34:46 PM »

hex barrel?

Never saw one with six sides. You must mean eight.



Had a guy from New England call me once about stocking a custom rifle he was having built.  He asked if I could inlet the forend for a "hex" barrel.  I said, surely you mean "octagon" barrel to which he replied "I can count to six, and my name ain't Shirley".  Turns out he had an old percussion chunk gun that had a by-gosh six-sided barrel, and he wanted the same on his cartridge rifle he was having built.  Still kinda shaking my head about that one...

Greg
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Don Getz
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« Reply #12 on: February 27, 2010, 04:54:26 PM »

You've brought up a subject that has intrigued me for a long time.    Many of you know Homer Dangler, he's been building
guns for I don't know how many years.  I  know he's probably over 80 right now, and, of all things, he probably still flying
airplanes.   I thought about making Homer a "hexagon" shaped barrel when filling an order for him, merely to hear his
comments after receiving it......just never had the guts to do it...........Don
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The other DWS
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« Reply #13 on: February 27, 2010, 05:11:21 PM »

it'd sure be fun to take a hex barrel to a match somewhere just to see how long it's be before someone actually saw to for what it was.

you could even do the stock up with pseudo-Penn-dutch art work inlays. Grin

seriously; I have always wondered about the whole octagonal barrel thing, where it originated and why.  My guess is there was an economic reason to start with---- then it became custom and tradition onto the machine age.
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g.pennell
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« Reply #14 on: February 27, 2010, 05:18:19 PM »

After I got that rifle stocked, I took it to several matches and passed it around for "show and tell"...it was one of the very first of the superb Frank Wesson No. 1 Long Range actions reproduced by Steve Earle.  Folks would just kinda look at it, knowing that something just wasn't quite right...then the light would go on!  "Hey, this thing has a six-sided barrel...!"

Greg
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