Polygonal rifling

[bornintheeu]

Hello everyone
I would like to know the advantages or disadvantages? Of a polygonal cannon weapon, such as the Tanfoglio, the Glock having according to my sources polygonal stripes which is not the same thing.

 

[jeepnik]

None. Just a different way of doing things. Throughout the years there have been many types of rifling. As long as they impart spin to the projectile to stabilize it in flight they are doing their job.

 

[Jim Watson]

The CLAIMED advantages for "polygonal" rifling are higher velocity - but only slightly higher and not in all cases as shown at Ballistics By the Inch - easier cleaning, and longer wear.
I SUSPECT the main advantage is longer tool life in hammer forge barrel manufacture, no sharp corners to chip under the impacts.

My sophomore geometry teacher would find fault with the term, "A polygon is a geometric figure bounded by STRAIGHT line segments." The gun barrels under the term are rounded in all directions. Different brands differ in detail.

 

[RX-79G]

I would definitely expect the greatest life from polygonal.

Glock's rifling is different. They called it "Cyclonic" at one time, and that profile can lead very badly. Which gave all polygonal rifling an unjustified bad name.

 

[bornintheeu]

None. Just a different way of doing things. Throughout the years there have been many types of rifling. As long as they impart spin to the projectile to stabilize it in flight they are doing their job.

Thank you

 

[bornintheeu]

The CLAIMED advantages for "polygonal" rifling are higher velocity - but only slightly higher and not in all cases as shown at Ballistics By the Inch - easier cleaning, and longer wear.
I SUSPECT the main advantage is longer tool life in hammer forge barrel manufacture, no sharp corners to chip under the impacts.

My sophomore geometry teacher would find fault with the term, "A polygon is a geometric figure bounded by STRAIGHT line segments." The gun barrels under the term are rounded in all directions. Different brands differ in detail.

Thank you for the information, for the polygonal term I agree with your teacher.
No doubt a contemporary version of the term.

 

[bornintheeu]

I would definitely expect the greatest life from polygonal.

Glock's rifling is different. They called it "Cyclonic" at one time, and that profile can lead very badly. Which gave all polygonal rifling an unjustified bad name.

Longer life OK, but from the point of view shooting offers you an advantage?

 

[RX-79G]

Longer life OK, but from the point of view shooting offers you an advantage?

"Shooting" is about accuracy, velocity and maybe recoil. Your typical polygonal bore may be slightly more accurate than your typical land and groove, but the most accurate bores are usually boutique land and groove barrels. The accuracy difference between any two barrels is virtually undetectable compared to the accuracy of the platform (9mm auto pistols don't shoot 3" groups because of the bore quality, but because of the fit and design of the action). Velocity is going to also be dependent on a lot more things than the rifling type.

So the reality is that polygonal bores aren't going to necessarily "shoot" any differently than any barrel. The benefits really come down to the quality for the price to manufacture, ability to deeply clean and (mainly) longevity.

I can't think of a polygonal bore pistol that doesn't have a good reputation for its barrel quality, so I would generally tend to favor such pistols. The production method that makes the bore polygonal offers other advantages in terms of barrel construction quality.

 

[bornintheeu]

Response relevant and very complete. Thank you very much.

 

[jeepnik]

"Shooting" is about accuracy, velocity and maybe recoil. Your typical polygonal bore may be slightly more accurate than your typical land and groove, but the most accurate bores are usually boutique land and groove barrels. The accuracy difference between any two barrels is virtually undetectable compared to the accuracy of the platform (9mm auto pistols don't shoot 3" groups because of the bore quality, but because of the fit and design of the action). Velocity is going to also be dependent on a lot more things than the rifling type.

So the reality is that polygonal bores aren't going to necessarily "shoot" any differently than any barrel. The benefits really come down to the quality for the price to manufacture, ability to deeply clean and (mainly) longevity.

I can't think of a polygonal bore pistol that doesn't have a good reputation for its barrel quality, so I would generally tend to favor such pistols. The production method that makes the bore polygonal offers other advantages in terms of barrel construction quality.

If more accurate why isn't it used on every bullseye & Olympic pistol?

 

[RX-79G]

If more accurate why isn't it used on every bullseye & Olympic pistol?

They have been used on some. But you didn't read what I posted:

Your typical polygonal bore may be slightly more accurate than your typical land and groove, but the most accurate bores are usually boutique land and groove barrels.

 

[Shaq]

The chronograph velocity charts I've looked at show a velocity increase of 40-60 fps at least in Glocks. The disadvantage is cast lead bullets shouldn't be used because of lead buildup which raises pressure.

 

[Deaf Smith]

Yes, it gets 5 percent or so velocity gain. If you added that with the Gerlich tapered bore principle, duplex/triplex powders, and increasing chamber pressures past the 65K cup (say 90k cup) you might get some real interesting velocities.

Real interesting velocities.

Deaf

 

[9mmepiphany]

... in Glocks. The disadvantage is cast lead bullets shouldn't be used because of lead buildup which raises pressure.

Note that the OP already mentioned that the thread did not include Glock's odd rifling

Also Post #4 expanded on the issue

Glock's rifling is different. They called it "Cyclonic" at one time, and that profile can lead very badly. Which gave all polygonal rifling an unjustified bad name.

 

[Dog Soldier]

I notice at the gun club Glock owners modify their pistols. They are buying drop in rifled target grade barrels. No, it is not just for cast bullets. I don't have a dog in this fight. I am just another "JAFO"

 

[RX-79G]

I notice at the gun club Glock owners modify their pistols. They are buying drop in rifled target grade barrels. No, it is not just for cast bullets. I don't have a dog in this fight. I am just another "JAFO"

Usually for lead concerns or to increase accuracy from barrel fit, rather than bore construction.

 

[AZAndy]

My only pistols with polygonal rifling are a pair of CZ-82s, and I can confirm the easier-to-clean aspect.

 

[bornintheeu]

Indeed this seems confirmed by all the owners of weapons with polygonal core, as well as speed.
Is reloading specific for ammunition in this type of weapon?

 

[jmr40]

Slightly better speeds, and easier to clean. While accuracy is probably on par with most conventional rifling I'd still put my money on pure accuracy from a match grade barrel with conventional rifling. Talking rifles here, probably not enough difference in pistols to matter.

I wouldn't be surprised to find that it is also cheaper to produce vs conventional rifling.

 

[bornintheeu]

This is interesting, if I understand correctly it is always the shooter that comes the precision.

 

[Jim Watson]

Is reloading specific for ammunition in this type of weapon?

It is commonly recommended not to load conventional wax lubricated lead bullets for Glock's "polygonal" barrels. It has been applied by extension to other brands of "polygonal" barrel, but perhaps RX-79G can give us some guidance on that, since he notes a difference from brand to brand.

I will note that SIG, even though they did not use "polygonal" rifling, still offered a dedicated barrel for lead bullets in the P210.

 

[Tirod]

The "why" that target barrels aren't using polygonal is based on in it being a radically different production method. Traditional rifled barrels use either a button die which passes down the barrel scraping the profile into the desired shape, or a toothed raker which takes one groove down the barrel at a time. Precision shooting barrel makers can do that with extremely low volumes - practically on a barrel by barrel basis - and keep pricing fairly low.

A polygonal barrel is almost always hammer forged - the barrel blank isnt finished shape or size, isnt precision bored to one of the finished land heights - it's basically a short fat slug of metal with a hole large enough to slip over a precision shaped mandrel. It's then precisely beat into the final shape of the exterior taper, which compresses the slug around the mandrel and forces it to conform, not only rifling it but also finishing it. Hammer forged barrels hot out of the machine don't have a smoothly lathed surface on them. And in comparison to the button or raker versions, come off by the dozens for the same amount of machine time.

Almost all First tier pistol barrels worldwide are now hammer forged, most rifle barrels are, too. It's the American military specification that lags because Colt dragged their feet on a multimillion dollar investment for a barrel forger, and the 2moa requirement plus military use pattern don't get a significant increment in user performance. However, for a competition shooter, the traditional button rifled barrel can deliver an incrementally better performance in scoring and that is where people like to escalate their expenses in order to win.

 

[Drail]

If you own a S&W revolver made since 96 it has polygonal rifling.

 

[ATLDave]

The only gun that I have with polygonal rifling is one of my Tanfo's. I would say it is easier to clean, except that I do not clean pistol barrels. When I look down the bore, it does look a little cleaner than some of my land-and-groove pistol barrels. The gun is very accurate, but my similar Tanfo's with land-and-grove barrels are also very accurate. I don't fool with bare lead bullets much, so I have no real input on the leading issue.

 

[Jim Watson]

I didn't know that.
S&W rifles their Monster Magnums by ECM with a gain twist, too.

Lothar Walther is the only maker I know of selling "polygonal" barrel blanks that you could profile, chamber, and hard fit a barrel to true match quality, just to see if it would keep up with land and groove. Interesting to me that most are a bit smaller groove diameter than standard.