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Posted: 7/22/2021 7:58:34 AM EDT
Several pistols use polygonal rifling, H&K, Desert Eagle, glock, etc..
I always read that it gives a slight accuracy edge over traditional rifling (in pistols anyways). Also easier to clean, supposed to give a better seal around the bullet, and last longer.
So I was wondering why it is not more commonly used on rifle barrels? I know there are a few manufacturers that make them, but they are few and far between compared to regular rifling. The reviews of them always seem to be great.
I am not talking specifically about AR barrel, but rifle barrels in general (semi auto and bolt action).

Are they just more expensive to make? Are they less accurate in rifles compared to cut rifling, or what?
When reading about it online I see many pros, but hardly and cons. I figure there has to be be several or at least one main big deal breaker to make them not more widely used. I am just curious what they are.
Link Posted: 7/22/2021 8:04:01 AM EDT
They used to be more common than they are now; for example, the Martini-Henry uses a form of polygonal rifling.

I suspect it just doesn't stand up well to the increased pressure of smokeless rifle rounds. The Brits had this issue with the Lee-Metford rifles (which used the same sort of rifling the Martinis had) and Cordite .303; it shortened barrel life dramatically.
Link Posted: 7/22/2021 8:05:45 AM EDT
If it improved accuracy, the match guys would be using it.

They don't, so I suspect it doesn't.
Link Posted: 7/22/2021 8:23:20 AM EDT
[Last Edit: 7/22/2021 8:30:28 AM EDT by JPC]
HK rifles also used it.
There were some AR barrels for awhile.
They were accurate.
Easier to ,do, button  cut rifling,,or "hammer forged".
Polygon ses harder,or rather fewer barrel manufacturers do it. They can be found.

https://vtsupply-com.3dcartstores.com/Black-Hole-16-556-M4-Carbine-750-1-8-Polygonal-Rifling-Barrel_p_1261.html

https://columbiariverarms.com/rifiling-manufacturing-process/
Link Posted: 7/22/2021 8:24:42 AM EDT
[Last Edit: 7/22/2021 8:25:22 AM EDT by heavymetal762]
Remington's famous 5R rifling was a form of polygonal rifling, and polygonal rifling is simply a more difficult and expensive process than conventional rifling, and it is less well-known here.

It's a lot like gain-twist rifling... some people notice benefits, some don't. Bartlein does gain-twist, and has great success with it. Black Hole Weaponry barrels were/are polygonally-rifled, and they are well-known for superior accuracy with match shooters.

It's a lot like brand loyalty.... not everyone is willing to honestly try different things.

I have both conventionally-rifled and polygonally-rifled barrels which are match-quality. I do find the polygonally-rifled barrels to be a bit more consistent, especially in high round-count circumstances (they don't retain fouling to the same degree as conventional barrels).
Link Posted: 7/22/2021 8:27:20 AM EDT
Is Black Hole Weaponry still around?
Link Posted: 7/22/2021 8:28:46 AM EDT
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Originally Posted By yamahawarrior89:
Is Black Hole Weaponry still around?
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Under a different name I think. I have one of their 6x45 barrels.
Link Posted: 7/22/2021 8:28:46 AM EDT
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Originally Posted By TacticalGarand44:
If it improved accuracy, the match guys would be using it.

They don't, so I suspect it doesn't.
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Yep.  Look at what the guys who win titles use.  If it helped they’d be using it.
Link Posted: 7/22/2021 8:43:56 AM EDT
Triarc uses polygonal rifling in their Track 2.0 barrels.  I just got an 11.5 one and tested it out yesterday.  M855 was not great from it, but M193 did well.  I did see some tests of theirs that seemed to give the edge to heavier bullets.  I used AE and IMI, seemed to work.  Using a TA31f on it, not using it for precision.  It was an  in stock barrel instead of a 6 month wait for a Criterion Core so giving it a go.

Triarc Systems 11.5
Link Posted: 7/22/2021 8:45:42 AM EDT
I had one in a wylde clambering. After 1400 rounds it was keyholing!
Link Posted: 7/22/2021 9:02:58 AM EDT
I have a polygonal LW barrel and I think my Larue Stealth barrel is polygonal.

They're not the most accurate barrels I own.  The LT might be the best value barrel I own since they were relatively inexpensive for a period of time.

I think the most important thing regarding barrel quality is that it's made in WI by the Obermeyer Industrial Complex
Link Posted: 7/22/2021 9:09:27 AM EDT
Originally Posted By Jeeps-And-Guns:

I always read that it gives a slight accuracy edge over traditional rifling (in pistols anyways)....
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It doesn't improve accuracy. It provides a sight increase in velocity because the bullet makes a better seal in the barrel.
Link Posted: 7/22/2021 9:14:47 AM EDT
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Originally Posted By GrimEReaper:
I had one in a wylde clambering. After 1400 rounds it was keyholing!
View Quote


It happens. Higher velocity and a wider range of bullet lengths can lead to issues with polygonal rifling.

Plus the cost savings in manufacture only seems to show up with short - as in pistol length - barrels.
Link Posted: 7/22/2021 9:15:33 AM EDT
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Originally Posted By yamahawarrior89:
Is Black Hole Weaponry still around?
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Yeah, but operating under their parent-company Columbia River Arms. Same people from what I understand. Barrels are still marked with the BHW logo.
Link Posted: 7/22/2021 9:19:12 AM EDT
Noveske
Link Posted: 7/22/2021 9:24:07 AM EDT
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Originally Posted By Third_Rail:


It happens. Higher velocity and a wider range of bullet lengths can lead to issues with polygonal rifling.

Plus the cost savings in manufacture only seems to show up with short - as in pistol length - barrels.
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Originally Posted By Third_Rail:
Originally Posted By GrimEReaper:
I had one in a wylde clambering. After 1400 rounds it was keyholing!


It happens. Higher velocity and a wider range of bullet lengths can lead to issues with polygonal rifling.

Plus the cost savings in manufacture only seems to show up with short - as in pistol length - barrels.


Great, never knew this, just got it, guess I'll have to keep an eye out on it.
Link Posted: 7/22/2021 9:26:00 AM EDT
Arisakas had Metford rifling, and many had a chrome-lined bore as well.
Link Posted: 7/22/2021 10:47:52 AM EDT
[Last Edit: 7/22/2021 10:51:35 AM EDT by Ryan_Scott]
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Originally Posted By dyezak:
Noveske
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Not really. They have “ratchet rifling” that’s more like a traditional groove with the edges knocked off asymmetrically.
Link Posted: 7/22/2021 10:51:03 AM EDT
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Originally Posted By heavymetal762:
Remington's famous 5R rifling was a form of polygonal rifling, and polygonal rifling is simply a more difficult and expensive process than conventional rifling, and it is less well-known here.
View Quote

Remington is more like traditional rifling with grooves that aren’t cut at 90 degrees.
Link Posted: 7/22/2021 10:51:31 AM EDT
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Originally Posted By Ronnoc:


Great, never knew this, just got it, guess I'll have to keep an eye out on it.
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Originally Posted By Ronnoc:
Originally Posted By Third_Rail:
Originally Posted By GrimEReaper:
I had one in a wylde clambering. After 1400 rounds it was keyholing!


It happens. Higher velocity and a wider range of bullet lengths can lead to issues with polygonal rifling.

Plus the cost savings in manufacture only seems to show up with short - as in pistol length - barrels.


Great, never knew this, just got it, guess I'll have to keep an eye out on it.


It's not a huge problem. Just don't stray from the "standard" length (in terms of the actual contact surface of the bullet) projectile for the caliber.
Link Posted: 7/22/2021 12:07:17 PM EDT
Based off the replies, it kinda seems like it is hit or miss with the barrels.
Seems like they are either loved, or they had issues.
Link Posted: 7/22/2021 12:28:35 PM EDT
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Originally Posted By Jeeps-And-Guns:
Based off the replies, it kinda seems like it is hit or miss with the barrels.
Seems like they are either loved, or they had issues.
View Quote

It boils down to manufacturing cost - polygonal rifling is hammer forged/formed over a mandrel, which is great for mass production.  If you aren't producing enough to take advantage of the economies of scale, it becomes less attractive as a fabrication method since there are no distinct performance gains to offset your costs.  I haven't tried it on my machines, but I bet I could make an extremely accurate (dimensionally) rifled pistol barrel with a CNC turning center, saving the investment in tooling and machinery costs associated with forging polygonal barrels.
Link Posted: 7/22/2021 12:54:43 PM EDT
[Last Edit: 7/22/2021 12:56:48 PM EDT by warlord]
Not an expert, but I think it is cost, and productivity, ie how many they make per hour.

The old site sponsor, the now defunct Olympic Arms used to have 2 riflings for their AR guns, button and cut.  According to the guy I forget his name now, to make a button riffling  that have a carbide broach that they shove down a drilled barrel under tremendous hydraulic pressure, one pass and ta da! one 1/9 barrel.  Cut rifling requires multiple passes. Their production SUM barrels were shooting 0.5" shot groups at 100yds.

ETA: SUM=stainless steel ultra match
Link Posted: 7/22/2021 1:26:58 PM EDT
Not an expert but the cost of a rifling machine vs the initial purchase of a hammer forging machine are probably similar but as someone mentioned, you can turn out hammer forged barrels by the thousands very quickly.

Hammer forging has several drawbacks

It creates a great amount of stress in the steel causing warping after a few rounds are fired which is the main reason why its not used for rifles very much. I read that the Steyr SSG sniper rifle used hammer forged barrel that were pressed into the receiver. It did not have a reputation for great accuracy after heating up.

Cut rifling is still the least stressful way to cut rifling and is also the most expensive due to the labor/time involved. Also make the most accurate barrels.

Canada(Diemaco) used to hammer forge their C7 barrels not sure if they still do.  
Link Posted: 7/22/2021 1:30:53 PM EDT

Exhibit A
Link Posted: 7/22/2021 1:42:07 PM EDT
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Originally Posted By Ryan_Scott:


Not really. They have “ratchet rifling” that’s more like a traditional groove with the edges knocked off asymmetrically.
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Pepperidge Farm remembers when Noveske only used Pac-Nor toobs.
Link Posted: 7/22/2021 1:51:52 PM EDT
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Originally Posted By dyezak:
Noveske
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I have an 18" SPR barrel, they used 5R rifling in their stainless barrels, not true polygonal rifling.  

This is from Faxon but the concept is the same in Noveske barrels:  5R has lands opposite grooves, and the angle at the top of the land isn't as sharp as a conventional barrel:




This is polygonal rifling:

Link Posted: 7/22/2021 1:58:13 PM EDT
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Originally Posted By warlord:
Not an expert, but I think it is cost, and productivity, ie how many they make per hour.

The old site sponsor, the now defunct Olympic Arms used to have 2 riflings for their AR guns, button and cut.  According to the guy I forget his name now, to make a button riffling  that have a carbide broach that they shove down a drilled barrel under tremendous hydraulic pressure, one pass and ta da! one 1/9 barrel.  Cut rifling requires multiple passes. Their production SUM barrels were shooting 0.5" shot groups at 100yds.

ETA: SUM=stainless steel ultra match
View Quote

Olympic broached barrels. Think of it as multi point cut rifling that is done similarly to the button rifling process.
Link Posted: 7/22/2021 11:17:23 PM EDT
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Originally Posted By spartacus2002:


I have an 18" SPR barrel, they used 5R rifling in their stainless barrels, not true polygonal rifling.  

This is from Faxon but the concept is the same in Noveske barrels:  5R has lands opposite grooves, and the angle at the top of the land isn't as sharp as a conventional barrel:

https://faxonfirearms.com/product_images/uploaded_images/riflingprofiles-zps0f29dd06.jpg


This is polygonal rifling:

http://www.sturmgewehr.com/bhinton/Heckler_Koch/PolygonalStandardRifling.jpg
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Originally Posted By spartacus2002:
Originally Posted By dyezak:
Noveske


I have an 18" SPR barrel, they used 5R rifling in their stainless barrels, not true polygonal rifling.  

This is from Faxon but the concept is the same in Noveske barrels:  5R has lands opposite grooves, and the angle at the top of the land isn't as sharp as a conventional barrel:

https://faxonfirearms.com/product_images/uploaded_images/riflingprofiles-zps0f29dd06.jpg


This is polygonal rifling:

http://www.sturmgewehr.com/bhinton/Heckler_Koch/PolygonalStandardRifling.jpg

Cool, I never knew what 5R was...
Link Posted: 7/23/2021 7:50:52 AM EDT
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Originally Posted By Ranxerox911:

It boils down to manufacturing cost - polygonal rifling is hammer forged/formed over a mandrel, which is great for mass production.  If you aren't producing enough to take advantage of the economies of scale, it becomes less attractive as a fabrication method since there are no distinct performance gains to offset your costs.  I haven't tried it on my machines, but I bet I could make an extremely accurate (dimensionally) rifled pistol barrel with a CNC turning center, saving the investment in tooling and machinery costs associated with forging polygonal barrels.
View Quote


Not all poly rifling is hammer forged. Black hole weaponry is button rifled polygonal.
https://columbiariverarms.com/rifiling-manufacturing-process/

While it does not specifically say button in that link, it does not say hammer forged either. I then found a thread on another forum where someone from the company posted about their barrels and someone asked if it was hammer or button. They said button.
http://www.predatormastersforums.com/forums/ubbthreads.php?ubb=showflat&Number=1610592
Link Posted: 7/23/2021 9:54:45 AM EDT
[Last Edit: 7/23/2021 12:35:17 PM EDT by Ranxerox911]
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Originally Posted By Jeeps-And-Guns:


Not all poly rifling is hammer forged. Black hole weaponry is button rifled polygonal.
https://columbiariverarms.com/rifiling-manufacturing-process/

While it does not specifically say button in that link, it does not say hammer forged either. I then found a thread on another forum where someone from the company posted about their barrels and someone asked if it was hammer or button. They said button.
http://www.predatormastersforums.com/forums/ubbthreads.php?ubb=showflat&Number=1610592
View Quote

True enough, but judging from the comments here regarding performance, and lack of popularity over other forms of rifling, there doesn't appear to be any advantage (other than manufacturing by forging) to using it.  

From a manufacturing standpoint, broaching with a button die has its own issues, but is better suited to short-run or one-off production than hammer forging is. Also, I assume that the machinery to produce it is more readily available.
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