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Old September 1, 2014, 07:50 AM   #1
Pond, James Pond
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Polygonal rifling in rifles.

As far as I know there are none that use this rifling am I wrong?

It is said to seal the bullet better, give great velocity, accuracy and barrel life and suits jacketed bullets.

Why isn't it used if long-arms?
Is it a velocity thing?
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Old September 1, 2014, 08:53 AM   #2
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HK uses polygonal rifling, pretty sure there are a couple other European manufacturers as well.
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Old September 1, 2014, 09:29 AM   #3
Jim Watson
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Lothar Walther will sell you a "polygonal" rifled barrel for various guns or a blank that can be made to suit about anything. Once upon a time, they conceded that the polygonal would be slightly less accurate than conventional land and groove but would last longer. I doubt it would be enough to matter in a service or hunting rifle.
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Old September 1, 2014, 10:20 AM   #4
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I don't know why this is not popular. Whitworth developed it for his muzzle loading black rifles, and from what I heard, it worked well. Maybe jacketed don't slug up all that well.

It would be a problem to fabricate. More difficult than drilling a hole and running a broach through the tube.
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Old September 1, 2014, 10:30 AM   #5
Jim Watson
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Apples and oranges.
The Whitworth could be shot either with a fitted hard lead hexagonal bullet or a round soft lead bullet which would slug up to the hexagonal bore. Any road, the Whitworth was superceded by other rifling plans within five years. The .451" 20 twist layout was the big improvement over .577 Enfield, not the rifling.

Modern "polygonal" barrels are made with a cross sectional area close to that of the bullet so they are a force fit, just as with land and groove.

I figure "polygonal" barrels are easier to make by modern hammer forge machines than "crisp" land and groove.
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Old September 1, 2014, 10:32 AM   #6
Art Eatman
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I'd bet that the vast majority of all shooters never wear out a barrel, so comparative durability would not be an issue. Again, opinion, accuracy is probably the primary requisite for this majority.
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Old September 1, 2014, 10:34 AM   #7
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Polygon rifled barrels cost half as much to make than other types once the barrel blank is gun drilled to some rough bore diameter. That's why they're popular in many service rifle barrels. But they've yet to equal the best of button, broach, hammered or cut rifled ones for accuracy.
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Old September 1, 2014, 10:45 AM   #8
Slamfire
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Quote:
I figure "polygonal" barrels are easier to make by modern hammer forge machines than "crisp" land and groove.
Once you buy the forge machine. I heard they are in the millions!

Post 8 of this thread, the poster has had interesting experiences with hammer forged barrels:

http://www.waltherforums.com/forum/p...tml#post100301
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Old September 1, 2014, 11:11 AM   #9
Jim Watson
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Split like a soda straw, huh?
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Old September 1, 2014, 11:23 AM   #10
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A metallurgist might be able to tell what really happens !
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Old September 1, 2014, 01:31 PM   #11
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I have a polygonal-rifled barrel on an AR-15 upper receiver.

Black Hole Weaponry makes them from raw bar stock in St. Helens, Oregon. The company just upgraded and updated their website, so it looks like most of the information on their polygonal rifling is missing. But... it's a three-groove 'clover leaf' pattern, like their logo - just not as pronounced.

They're reported to be fantastic barrels. But, mine has not yet been tested...
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Old September 1, 2014, 01:34 PM   #12
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Arisaka type 38.

-TL
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Old September 1, 2014, 01:48 PM   #13
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Quote:
Originally Posted by Jim Watson
Apples and oranges.
The Whitworth could be shot either with a fitted hard lead hexagonal bullet or a round soft lead bullet which would slug up to the hexagonal bore. Any road, the Whitworth was superceded by other rifling plans within five years. The .451" 20 twist layout was the big improvement over .577 Enfield, not the rifling.

Modern "polygonal" barrels are made with a cross sectional area close to that of the bullet so they are a force fit, just as with land and groove.
I recon that another advantage of the Whitworth's hexagonal bore is being nearly smoothbore-easy to clean the fouling out of.
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Old September 1, 2014, 02:03 PM   #14
Jim Watson
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Whitworth furnished a hexagonal scraper to get the worst of the fouling out.

As I said, within five years, Whitworth was largely supplanted by Gibbs, Alex Henry, and other rifling plans. The pentagonal and heptagonal rifling brought out in emulation of Whitworth did not last, either.

I put "polygonal" rifling in quotes because my sophomore geometry teacher said a polygon is a geometrical figure bounded by straight line segments. No straight lines to be seen down a Glock barrel. Metford did well with that wallowed out looking design until Cordite came along. Arisaka made it heavy enough to last.

I am still waiting for the return of Lancaster oval bore, the ultimate in low friction and easy cleaning.
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Old September 1, 2014, 09:34 PM   #15
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Disregard....
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Old September 2, 2014, 03:28 AM   #16
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Doesn't LaRue make some of their rifles with polygonal rifled barrels?
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Old September 4, 2014, 03:32 PM   #17
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Quote:
Doesn't LaRue make some of their rifles with polygonal rifled barrels?
Used to... I don't think any of their current models feature it.

Polygonal never caught on much. Always looking for a better mousetrap, there was a lot of hype around Rem's 700 milspec with 5R rifling when released. Hey, same barrel as the M24 SWS used by the military. But reality eventually trumped hype, and while some were no doubt "believers", many noticed no advantage over traditional lands and grooves.
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Old September 4, 2014, 03:46 PM   #18
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Well, 5R is not "polygonal" in the Glock usage. It is what the old Brits (there they are again) called "trough shaped rifling." There are several sources if that is what you think you need. Mostly it is quality not the number or exact shape of the grooves.
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Old September 5, 2014, 06:12 AM   #19
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Yeah, I know... I should have explained better. I was just referring to another "different" type of rifling, that never really caught on. Thanks for clarifying.
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Old September 5, 2014, 06:59 PM   #20
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Quote:
Originally Posted by Jim Watson
Well, 5R is not "polygonal" in the Glock usage. It is what the old Brits (there they are again) called "trough shaped rifling."
Is this the "trough shaped rifling" you speak of?

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Old September 8, 2014, 06:50 AM   #21
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I have one of those Black Hole AR's with polygonal rifling and up to this point, I'm NOT impressed with it. Maybe just haven't found the right bullet or just haven't given it enough time. Right now, it's been collecting dust because an el-cheapo DelTon gives better accuracy.
I fell for the advertising of less fouling and higher velocities.
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Old September 8, 2014, 08:31 AM   #22
Jim Watson
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BLE, I can't be sure if that is trough shaped rifling or not, what with the slaunchways photo angle.
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Old September 8, 2014, 06:39 PM   #23
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BLE, I can't be sure if that is trough shaped rifling or not, what with the slaunchways photo angle.
The lands have sharp edges but the bottoms of the grooves are kind of round. This is the barrel of a muzzleloader I own, I'm not sure who made the barrel. I guess the idea was to make the fouling easier to clean out of the barrel, no 90 degree corners for fouling to hide in.
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Old September 8, 2014, 06:57 PM   #24
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Steyr Mannlicher has polygonal rifling, iirc, and it shoots pretty well in my experience.
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