Glock barrels, why polygonal rifling?

[gamestalker]

I bought my first, and I think my only Glock back in the 1980's, a G17. At that time there were a couple rumor's floating around that Glock barrels were made of a hi tech non metallic carbon material, or that they were a chrome lined chi tech carbon material, of course is probably due to the term "polygonal" being misapplied.

Anyway, all that said, what is the advantage of polygonal rifling verses standard land & groove rifling. And do other firearm manufacturer's use polygonal rifling. I did a bit of research on polygonal rifling, and apparently it was first introduced back in the 1800's, but I didn't entirely understand whether it offered a ballistic advantage or not. And if it does, why isn't it being commonly used more often.

GS

 

[Zaydok Allen]

It typically yields a bit more velocity, though not much more.

HK uses polygonal rifling as well.

 

[dogtown tom]

gamestalker ..... At that time there were a couple rumor's floating around that Glock barrels were made of a hi tech non metallic carbon material, or that they were a chrome lined chi tech carbon material, of course is probably due to the term "polygonal" being misapplied.

You can thank Detective John McClain in Die Hard 2:

That punk pulled a Glock 7 on me. You know what that is? It's a porcelain gun made in Germany. Doesn't show up on your airport X-ray machines, here, and it cost more than you make in a month.

I have one neighbor that still thinks Glocks are invisible to x-rays.

 

[tarosean]

Cost effective would be my best guess..

 

[gruney]

Because it sounds cool

Kahr uses on premium models. IIRC my Bersa T9UC has it too.

It's supposedly has better gas sealing, but I think it's faster because of less friction. Glock uses hexagonal for smaller calibers and octagonal for 45 caliber.

I think it's easier to clean because you don't have all those 90 degree angles in the grooves to trap crud.

Never heard a good explanation of why Glock used it, but maybe it was lower production cost. Or Gaston got a deal on a barrel rifling machine and figured that along with the ceramics it would differentiate his pistols.

 

[chicharrones]

My CZ82 has polygonal rifling, too.

I like that type of rifling for ease of cleaning for sure. It seems like all you have to do is swab it out. Glock only supplies a nylon brush with their pistols, so I guess they figure it is easy to clean as well.

 

[usp9]

Better gas seal with the bullet
Easier to clean
Longer life
Looks better, (I made that part up).

 

[Thompsoncustom]

I would assume it's cheaper for them to produce

 

[Zerodefect]

-easier to clean
-easier to consistently produce well using a hammer forge

Glock makes a ton of barrels. Consistency is one of the greatest thing about Glocks. Need sights? I can email my sight setup to someone clear across the country an it'll work perfectly. Can't do that with my 1911's.

It surely wouldn't work in rifles?

 

[ATLDave]

There have been artillery pieces with polygonal rifling. Sure, they can be used in rifles.

 

[Wireman]

Like anything else there must be pro's and con's, but more consistent bullet obturation seems like the obvious benefit. One specific area that polygonal rifling may have the advantage is at the muzzle due to more even gas sealing (if that in fact is the case). Smooth lands stress the metal less than traditional rifling, resulting in less tendency to collect fouling. Those are my guesses. HK must have a very good reason and they are not known for cutting corners where reliability is concerned.

Wire

 

[Zaydok Allen]

I do really love how easy they are to clean.

 

[ATLDave]

I have a non-Glock pistol with polygonal rifling. I have no idea whether it is easier to clean because I do not clean pistol barrels.

 

[kokapelli]

I would assume it's cheaper for them to produce

If that were the case why is it used mostly in expensive pistols?

This link has some good info.....
https://en.m.wikipedia.org/wiki/Polygonal_rifling

 

[9mmepiphany]

I didn't realize how may misunderstandings there were about polygonal rifling

It surely wouldn't work in rifles?

Well, my first H&K rifle (HK-91; 7.62x51mm) had polygonal rifling as did their 5.56x45mm version as well as their light and medium machine guns. As a matter of matter, at one time, all the guns in their lineup used polygonal rifling...including their sporting rifles.

I've owned 4 H&Ks with polygonal barrels...HK-91, HK-93, P9S, and P7

I would assume it's cheaper for them to produce

Yes and No.

While the cost per barrel is likely cheaper, the investment in the machinery to produce them is much more expensive. That is why you'll only see polymer barrels on mass produced guns

And do other firearm manufacturer's use polygonal rifling.

The CZ is the earliest that I've ever shot, but the most common ones are H&K and Kahr.

BTW: the rifling that Glock uses in the G17 isn't a "true" polygon bore...as their "Flats" actually have a lead

but I didn't entirely understand whether it offered a ballistic advantage or not.

Due to it's better seal around the bullet, the polygonal bore is supposed to offer higher velocity, better accuracy, and easier cleaning.

I remember reading that the polygonal bores were birthed during the muzzle loader period...less fouling...but I don't remember the dates given and can't cite a source

 

[JohnKSa]

The Whitworth rifle had polygonal rifling and used a matching bolt/projectile already shaped to fit the polygonal shape of the bore.

The article in the link below suggests that Whitworth invented polygonal rifling.

http://www.americancivilwarstory.com/whitworth-rifle.html

 

[Coyote3855]

"While the cost per barrel is likely cheaper, the investment in the machinery to produce them is much more expensive. That is why you'll only see polymer barrels on mass produced guns."

I'm sure 9mmepiphaney is not channeling John McClain and intended to say "polygonal" in his post.

 

[Zaydok Allen]

"While the cost per barrel is likely cheaper, the investment in the machinery to produce them is much more expensive. That is why you'll only see polymer barrels on mass produced guns."

I'm sure 9mmepiphaney is not channeling John McClain and intended to say "polygonal" in his post.

I saw that last night. I believe 9mm was a victim of autocorrect.

 

[9mmepiphany]

Yup, either that or just old age...this is the second brain fart from last night (I just removed a "k" from the last word).

I guess I could revert to old school proof reading

 

[teppo-shu]

Not yanking anyone's chain, but if you buy into the BBTI guys' work, the whole gas-seal, higher velocity thing would seem to be largely a myth, at least in 9mm:
http://www.ballisticsbytheinch.com/rifling.html

I own a couple of HKs and one Glock, and can attest to the ease of cleaning.

Best regards

 

[Elkins45]

So if it offers a better gas seal then why does it give such trouble with cast or (especially) swaged lead bullets? I bought my first Glock (19) in 1989 and I very quickly learned that shooting cast well in a polygonal barrel is a lot harder than with traditional rifling.

 

[9mmepiphany]

Sealing and bite into a soft bullet to impart spin are two different properties.

Lead tends to "skid/smear" across the planes of the polygon, whereas a jacketed bullet will just fill and start rotating

 

[silicosys4]

So if it offers a better gas seal then why does it give such trouble with cast or (especially) swaged lead bullets? I bought my first Glock (19) in 1989 and I very quickly learned that shooting cast well in a polygonal barrel is a lot harder than with traditional rifling.

Different people have different results.
I too had heard that polygonal barrels won't shoot cast bullets well, and if they did, they would blow up in your hand due to lead buildup.
For me, that hasn't been the case.
I never had an issue with leading in my cast loads with polygonal barrels. The best 25yard 10 shot group I've shot with a .45 was a Glock 21 with 200gr. cast handloads.
I have had Kahrs and currently own an HK USP45 and a Glock 19. All I have ever done is load and shoot my regular handloads, never worried about custom tailoring a load to any of my polygonal barrel guns, and never had an issue.
I do make a point to clean them regularly to avoid any chance of lead building up even though to this point I've seen very little to none.

 

[Jim K]

So-called "polygonal" rifling is pretty much the same idea as the old Metford rifling, which had rounded lands. It had the advantage of being easier to clean and more resistant to erosion, but in the end the British dropped it and the major user in WWII was the Japanese.

The normal right angle lands, when used with jacketed bullets, have the disadvantage that the jacket will not completely fill the grooves, leaving a triangle in the corner of the groove where fast-moving gas will erode the bore. This can be seen in almost any .45 pistol barrel that has seen much use with heavy jacket GI ammunition.

Jim

 

[dwhite]

The normal right angle lands, when used with jacketed bullets, have the disadvantage that the jacket will not completely fill the grooves, leaving a triangle in the corner of the groove where fast-moving gas will erode the bore. This can be seen in almost any .45 pistol barrel that has seen much use with heavy jacket GI ammunition.

Never thought of this but it makes great sense. You're just not going to swage that bullet into the very corners of the rifling. I can see this letting gas by.

Thanks for sharing.

All the Best,
D. White