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Very Hot Topic (More than 25 Replies) Round Barrel vs Oct/Round? (Read 2523 times)
bucksnort
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Round Barrel vs Oct/Round?
Dec 7th, 2018 at 2:07pm
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Is there any benefit or advantage that a straight round barrel would have or not have over a oct/round barrel? (This would be on a .32-40 CPA BR rifle)  Thanks.
  
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JLouis
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Re: Round Barrel vs Oct/Round?
Reply #1 - Dec 7th, 2018 at 2:26pm
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Probably personal preference for appearance I have both and they both shoot as well. Most all of my own personal accomplishments over the past seventeen years were while using a half oct. to round barrel. But I also like my round with a wee bit of taper that I have been using for the last three years. A straight barrel without taper does look a bit odd and out of place if it that might matter to you.

JLouis
  
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Amoretti
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Re: Round Barrel vs Oct/Round?
Reply #2 - Dec 7th, 2018 at 2:28pm
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I don’t know the answer but Sharps claimed it was proven round bbls were more accurate than octagon.  Maybe they were trying to save money and did not want to make them.  From Sellers book.

Personally I don’t think it would make a difference.

John

  
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Jeff_Schultz
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Re: Round Barrel vs Oct/Round?
Reply #3 - Dec 7th, 2018 at 2:34pm
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  A straight round blank is considerably cheaper, stiffer, and easier to index.
  

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Redsetter
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Re: Round Barrel vs Oct/Round?
Reply #4 - Dec 7th, 2018 at 2:44pm
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Jeff_Schultz wrote on Dec 7th, 2018 at 2:34pm:
  A straight round blank is considerably cheaper, stiffer, and easier to index.


But for a given weight, wouldn't the octagon be stiffer?
  
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Re: Round Barrel vs Oct/Round?
Reply #5 - Dec 7th, 2018 at 2:50pm
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There are two or three advantages (or detriments, if you like).

A straight round will have more weight than a tapered 1/2 octagon and a round barrel, will have more weight before it's machined it octagon.

I like straight barrels, whether octagon or round. Any thing you do to a barrel, should be done evenly.

Machining a barrel, can either relieve stress in the barrel, or create it, or even both!

I wouldn't ever taper a choked barrel, as that has the possibility to remove some of the choke.

Frank
  

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Re: Round Barrel vs Oct/Round?
Reply #6 - Dec 7th, 2018 at 3:08pm
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I believe the OP is having CPA doing the barrel work. But if doing his own and an Oct. Steve Durren has a great article that fully describes how easy it is to go about indexing one in the ASSRA Single Shot Rifle Journal Vol. 59, No. 2 March - April 2005 Page 26 & 27.
Also CPA's pre-turned and polished blanks are a real joy to work on I found the quality of the one I worked on for a friend to be outstanding. Just need to be careful and wrap it real good to protect the finish and when done with just a bit of tape adhesive removal it was ready for rust bluing.

JLouis
« Last Edit: Dec 7th, 2018 at 3:20pm by JLouis »  
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marlinguy
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Re: Round Barrel vs Oct/Round?
Reply #7 - Dec 7th, 2018 at 4:29pm
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Back to the original question. How you measure the diameter and taper will determine how full round, or half octagon compare.
If the round barrel is equal in diameter to the high points of the octagon, or equal to the measurement across the flats. A round barrel with a diameter equal to the flats on a half octagon will not be heavier, or stiffer. But a round barrel with a diameter equal to the high points of a half octagon will be both heavier and stiffer.
So which is better depends on the diameter, taper, length, of the particular barrel. And a octagon, or half octagon that is the same diameter across the flats as a round barrel, will be a little heavier, and a little stiffer due to the slightly larger corners of the octagon portion.
  

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Re: Round Barrel vs Oct/Round?
Reply #8 - Dec 7th, 2018 at 4:35pm
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And a octagon, or half octagon that is the same diameter across the flats as a round barrel, will be a little heavier, and a little stiffer due to the slightly larger corners of the octagon portion.


And if the round area is tapered as most are?

Frank
  

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marlinguy
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Re: Round Barrel vs Oct/Round?
Reply #9 - Dec 7th, 2018 at 4:41pm
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frnkeore wrote on Dec 7th, 2018 at 4:35pm:
Quote:
And a octagon, or half octagon that is the same diameter across the flats as a round barrel, will be a little heavier, and a little stiffer due to the slightly larger corners of the octagon portion.


And if the round area is tapered as most are?

Frank


Compare apples to apples. If the round portion of the octagon is tapered, that section is the same as the round portion of the round, if of equal diameters.
All of my factory barrels are tapered. Tapered on the octagon, round, or on round and octagon of the half octagon barrels. I don't know of any old barrel makers who didn't usually taper all three styles of barrels, unless a customer specifically requested no taper. Most have so little taper you need to measure them to discover it. But I have seen some in half octagon where the round section was tapered faster than the octagon section. Something you wouldn't do with a full round, as the change in taper would look weird. You'd have to just do a faster taper, or "pencil weight" barrel.
I have a couple half octagon pencil weight barrels, and they are extremely lightweight.
  

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Re: Round Barrel vs Oct/Round?
Reply #10 - Dec 7th, 2018 at 7:06pm
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All the octagon barrels I have owned taper about .008" per inch of barrel.

My round Palma target profile barrel tapers considerably more at .023" per inch of barrel.

It is a straight taper from the receiver to the muzzle.
« Last Edit: Dec 7th, 2018 at 7:13pm by Schuetzendave »  
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Re: Round Barrel vs Oct/Round?
Reply #11 - Dec 7th, 2018 at 7:55pm
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marlinguy wrote on Dec 7th, 2018 at 4:41pm:
frnkeore wrote on Dec 7th, 2018 at 4:35pm:
Quote:
And a octagon, or half octagon that is the same diameter across the flats as a round barrel, will be a little heavier, and a little stiffer due to the slightly larger corners of the octagon portion.


And if the round area is tapered as most are?

Frank


Compare apples to apples. If the round portion of the octagon is tapered, that section is the same as the round portion of the round, if of equal diameters.
All of my factory barrels are tapered. Tapered on the octagon, round, or on round and octagon of the half octagon barrels. I don't know of any old barrel makers who didn't usually taper all three styles of barrels, unless a customer specifically requested no taper. Most have so little taper you need to measure them to discover it. But I have seen some in half octagon where the round section was tapered faster than the octagon section. Something you wouldn't do with a full round, as the change in taper would look weird. You'd have to just do a faster taper, or "pencil weight" barrel.
I have a couple half octagon pencil weight barrels, and they are extremely lightweight.

Schuetzendave wrote on Dec 7th, 2018 at 7:06pm:
All the octagon barrels I have owned taper about .008" per inch of barrel.

My round Palma target profile barrel tapers considerably more at .023" per inch of barrel.

It is a straight taper from the receiver to the muzzle.

My Stevens 44, #3 part octagon barrel, 7 o'clock extractor, is 1.065 straight octagon. The round starts at 1.022 and tapers to .806, at the muzzle. That is the only, factory part octagon barrel, that I own and that is what I had in mind when I said the above.

I hadn't considered octagon tapering. I make all my octagon barrels straight, for increased weight. I came to SS from ML and I  personally, don't think octagons look, quite right, tapered.

Frank
  

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Re: Round Barrel vs Oct/Round?
Reply #12 - Dec 8th, 2018 at 9:37am
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In my opinion the more machining you do to a barrel the more stresses you run the risk of creating. I balance that with what the rifle is being built for. If it is a traditional rifle I prefer a full octagon but bench rest rifle I prefer to remove just enough stock to true the barrel to the bore and clean it up., that's it just the minimum.

40 Rod
  
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Re: Round Barrel vs Oct/Round?
Reply #13 - Dec 8th, 2018 at 10:37am
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Thanks Frank for confirming that the Steven's Octagon portion is straight on a part octagon. When I visited CPA tht is what Gail said and I was hopeing to get it confirmed. She said that is the way they do theirs too.

Also, Tapering a button rifled barrel is probably not a good idea since the compressive stresses get released as you turn them down and this could lead to a reverse choked barrel. THe opposite of Anschutz who leave the bulge at the muzzle to choke the barrel by relieving the stresses before the muzzle.

Charles
« Last Edit: Dec 8th, 2018 at 2:58pm by bohemianway »  
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Re: Round Barrel vs Oct/Round?
Reply #14 - Dec 8th, 2018 at 12:07pm
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My .218 Bee,.32-40, .40-65 WCF and .40-60 Maynard CPA Rifle barrels were full octagon with .008"/inch taper.

To most people they appear straight octagon without a taper until you measure them.
  
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