Polygonal Barrels & Fouling

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centralpadoug

New member
My understanding is that polygonal barrels (as in Glocks & H&K's) have somewhat rounded lands vs. the sharper lands on more conventional barrels. Logic tells me that a more rounded edge will not "cut" the bullet like a sharper edge will. If this is true, how is it then that polygonal barrels will be more prone to fouling from lead bullets (and pose a greater risk) than a jacketed bullet?

I have shot thousands of rounds of lead bullets through my H&K USP45 with no problem.
 
B

Badger Arms

New member
Polygonal rifling turns the bullet through friction and deformation while traditional rifling cuts the bullet. The same friction also pulls a little lead off if you are shooting soft lead reloads. Simply switch to hardcast bullets or use a harder alloy.

As for your personal experience, if you are casting your own and don't have any concept of hardness, you might get one soft batch and one hard batch and not know the difference. If you buy cast bullets, they are more consistantly hard and you shouldn't worry any.
 
G

George Helser

New member
Do Glocks have polygonal barrels? My G26 does NOT. The advertising says "hexagonal" barrel meaning 6 lands/grooves.

I own HKs with polygonal barrels and they have a unique look. I think the polygonal barrel is more expensive to make and gives less bullet friction resulting in higher velocity with less barrel wear.

Regards,
George
In sunny Arizona
 
C

Chad Young

New member
Mr. Helser,

ALL factory Glock barrels at this time use polygonal rifling. Your is listed as hexagonal because the shape formed by the rifling has six sides. Polygonal rifling does not have traditional lands and grooves, so its configuration is usually indicated by the approximate geometric shape of the bullet's path - in this case, a hexagon.

I beleive that H&K pistols frequently use polygonal rifling. Easier to clean and generally gives higher velocities out of identical length barrels.
 
E

Elmo

New member
Polygon = A closed plane figure bounded by three or more line segments.

Hexagon = A polygon having six sides.

Octagon = A polygon having eight sides.

Triangles are polygons.
Squares are polygons.
Hexagons are polygons.
Octagons are polygons.

...and so on.... :)
 
W

Walt Sherrill

New member
Badger had the best explanation. Put another way, because the barrel is hexagonal, it uses bullet contact with the flats of the hexagon (which are the sides of the barrel); because the hexagon is twisted, that contact imparts the spin -- and not contact with lands in the barrel.

This means that MUCH more of the bullet is in contact with the barrel and there is more bullet surface to be eroded resulting in more lead to build up.

My son, a cop, used my Glock 17 in his police certification training. They were shooting lead bullets. We cleaned it each night, very conscious of the potential problem with lead build-up, got the lead out (it was noticeable but not too bad). He had no problems and also had the highest scores in the class. (Of course, everyone else -- except a full-time cop -- was shooting worn-out S&W semis provided by the college.)

If you REALLY want to shoot lead in a Glock, get one of the traditional barrels avaialble from any number of sources. Bar-Sto has them, as do others.
 
O

Old Reb

New member
Polygonal barrels are not cheaper to make. You won't see any replacement barrelmakers using this method for good reason -- it's too expensive. Polygonal barrels are cold hammer forged around a precisely sized mandrel, which is the strongest of the various barrel designs. Like the barrels used in some very expensive sniper rifles, this forms both the chamber and rifling in one single operation. The barrels must then be carefully machined to final external dimensions.
 
L

leedesert

New member
All Glocks are polygonal, meaning multiple sides.

All calibers except for 45 and 10mm are hexagonal(6 sides).

The 45 and 10mm are octagonal (8 sides) because of the larger caliber requiring more barrel contact.

Glocks do not have lands/grooves. This is a term used for rifled barrels.

Do some homework guy's before giving advice.
 
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George Helser

New member
OK, Every gun has a polygonal barrel because it has multiple sides.

HK uses the term polygonal to define the barrels in its P7s (and some other models) as being different from the simple, traditional barrel rifled with distinct lands/grooves.

My G26 has a simple, traditional rifling with distinct lands/grooves like my S&Ws, Colt and almost all other arms made. It does NOT have the smoothly graduated rifling of a
P7. If you wish to use the term polygonal to describe any rifling, how do you define the rifling in a P7?

Regards,
George
In sunny Arizona
 
T

Thumper

New member
George...

Respectfully...If you still have a factory barrel in your Glock 26, it is in a polygonal (hexagonal, to be more precise) configuration.

If you look through the barrel, this can be misleading because if you don't look carefully, the angles almost appear as lands and grooves. But trust me, unless you've put an aftermarket barrel in it, your 26 utilizes hexagonal rifling.

In fact, if you go here:

http://www.glock.com/g26.htm

You'll note that under barrel, the official glock page lists it's type as right(twist),hexagonal.


Gaston wouldn't have it any other way.
 
O

Oris

Moderator
Old Reb,

Tooling for forming the rifling is much more expensive
due to the complexity of tool profile and the number of operations required to produce rifled barrel is greater than the number of operations to produce polygonal barrel. This makes production of polygonal barrel cheaper. You might want to consult some tooling/manufacturing engineers.
Current fashion for polygonal barrels is a matter of cost
reduction. BTW, if I recall it correctly, the first
guns which were shooting "twisting bullets" had polygonal barrels - it was something that could be done w/o using
modern hitech methods and precision tools.
 
C

centralpadoug

New member
Walt Sherrill had the same results I have seen. I guess the bottom line is that the lead used needs to be hard cast as I am currently using. It has resulted in VERY accurate groups, no feed or fouling problems. While expense is not the only concern, it is nice that they only cost $16 for 500 at my local gun shop.

It's interesting to hear the various ideas regarding the different technology (or in some cases, lack of technology) that applies to these barrels. I know an older gentleman that swears by conventional rifling such as Springfield Armory uses in its 1911's. He views such newer guns as Glocks, & H&K's as not nearly as effective (he's a bullseye/PPC shooter). I like to shoot my H&K for everything from PPC to steel to IDPA...maybe when I can afford a gun for every game I'll come back to his approach. For now I am very happy with the results of some good old fashioned hard cast lead through a very accurate and reliable H&K!

Thanks for all the excellent ideas and good conversation!
 
B

Badger Arms

New member
Oris, Old Reb:

Actually, Rifling is cheaper to tool up for but it's more expensive to produce. Polygonal is very expensive to tool up for but much cheaper to produce once you are tooled. Polygonal rifling is produced through hammer forging where a blank is beat into shape over a precision ground mandrel. This mandrel is all that needs to be changed (along with the hammering machine settings) to change the bore size and twist rates.

Traditional Ballard type rifling requires a tool that cuts the inside of a barrel. This cutting process leaves burrs and stress concentrations on the inside of the barrel. The tooling must be replaced and consistancy has been the bane of barrel-makers for centuries.

As to which is superior, Polygonal rifling is proported to yield about 5% greater velocity, easier cleaning, cheaper mass production, and lasts forever... almost. Ballard rifling is more accurate, more resistant to fouling, has a die-hard following, and lasts about half as long as Polygonal.

Take your pick.

For the record, traditional rifling can also be produced by hammer forging.
 
O

Oris

Moderator
Badger Arms, thanks. But that's what I'm talking about -
polygonal barrels are cheaper to produce. In regard to
arbors for polygonal barrels - sure, they need to be made from high quality heat resistant materials, but you would agree, that precision broaches for forming the rifling are not cheap either, and on top of this, gun drilling, when needed, is pretty slow...
 
D

Doug 29

New member
Hmmmmmmm..........I thought almost all barrels, today, were produced using the hammer-forged method. Cut-rifling belongs in the stone-age!
 
H

hksigwalther

New member
Well, from examining the barrels of my HKs and my one Glock, here's how I would characterize the rifling.

The HK's are true equilateral polygonals (polygon with identical flat side lengths) with slightly rounded corners.

The Glock is like regular land/groove except the lands are rounded and not square. Much like a very low setting sun in the horizon. Where the curved 'land' meets the 'groove', the corner is not sharp. Not a true polygon, but close enough to call it one as it is more like a polygon than land/groove.
 
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Badger Arms

New member
Tooling for conventional cut rifling is relatively cheap but the process is much more expensive. The majority of barrels currently are traditional cut-rifling. Hammer Forged barrels are making up ground and will eventually overtake but it'll be a few years. By tooling, I'm speaking of more than just the cutters. I'm speaking of the boring machines, gagues, and most importantly, the skilled labor. Once the tooling up is done, hammer forged barrels can be 'stamped' out in quantity and more cheaply.
 
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