polygonal barrels


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moooose102
May 26, 2008, 02:31 PM
so what is the deal with the polygonal barrels. i have seen this mentioned several times before. i do not know what they are, and how they make for a better gun. or do they? or is it just another ploy to sell guns.

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jocko
May 26, 2008, 02:34 PM
more expensive to produce. no more accurate, supposed to be an increase in velocity with a polygonal bbl, how much is another thing. Have to be careful shooting lead out of one though, needs to be throughly cleaned. Glock does not recommend it, kahr also does not recommend lead. Normally a polygonal rifled barrel is a more quality type barrel also.

blkbrd666
May 26, 2008, 02:40 PM
What modern handguns use polygonal rifling?

NG VI
May 26, 2008, 03:00 PM
Glock OEM barrels are 'hexagonal', same idea, similiar execution, H&K uses them, IMI/Magnum Research Baby Eagles, not sure who else uses them.

They supposedly give a boost to velocity and accuracy potential because of the increased bullet to bore contact, but I'm not sure how big the gain is.

possum
May 26, 2008, 03:08 PM
glock, h&k, also kahr iirc.

stay away from using kead loads in these types of barrels, or just insure that you clean them really well and remove all the lead fouling when you clean.

atblis
May 26, 2008, 05:41 PM
Tanfoglio seems to use them sporadically.
CZ uses them on occassion (CZ82)

more expensive to produce.
Not necessarily. The equipment itself is expensive, but if you're producing enough barrels, it is very economical for cranking out mass quantities (like Glock).

gaowlpoop
May 26, 2008, 08:07 PM
This is a good explanation.

http://en.wikipedia.org/wiki/Polygonal_rifling

Jim Watson
May 26, 2008, 08:54 PM
As to manufacturing cost, I suspect a hammer forge mandrel with gentle curves will last longer than one with sharp corners. All the stuff about higher velocity and longer barrel life is a case of making a virtue out of necessity.

Shadow1198
May 27, 2008, 12:59 AM
Here's an example of polygonal rifling:

http://www.fullaventura.com/municiones/fotos/municiones102119_4.jpg

Technically, it does actually increase the velocity of the bullet as true polygonal rifling does not use lands and grooves and provides a better gas seal. It's not some drastic difference or anything but, it definitely does make one. Not to mention, generally it's easier to clean a true polygonal rifled barrel as there aren't lands and grooves so it is much easier to scrub everything off with a bore brush. The whole issue with not being able to shoot lead bullets through polygonal barrels is entirely due to the increased fouling present with lead bullets. I don't fully understand it but, apparently it's easier for fouling to build up with a polygonal barrel. If there is too much build up it can lead to severely increased muzzle pressure, which could in turn cause a kB.

jlh26oo
May 27, 2008, 05:28 AM
Glock OEM barrels are 'hexagonal', same idea, similiar execution, H&K uses them, IMI/Magnum Research Baby Eagles, not sure who else uses them.


Glock .45's are octagonal, everything else is hexagonal, and both types are polygonal (I.E. hexagons and octagons are both polygons A.F.A.I.K.)! I like it, especially to make up for some lost velocity in compacts and subcompacts (I.E. kahr)! But it's not as big a factor for me in a full size.

DWARREN123
May 27, 2008, 05:48 AM
My GLOCK barrels seem to stay cleaner with jacketed or plated bullets and they are pretty accurate. I don't know if they really do make a lot of difference but they work as good as regular rifling.

jocko
May 27, 2008, 07:25 AM
Other than they all say stay away from lead bullets. i see no downside to the polygonal barrel. If its better, I like it. My little 3" kahr pm9 barrel can use all the extra git-up and go with a polygonal bbl, and that is fine with me. the theory sure sounds reasonable.

usp9
May 27, 2008, 07:49 AM
Here's a great shot of a polygonal barrel, (can you name the firearm :scrutiny:)
Personally I don't think they are "better', just a different way of spinning the bullet. The main advantage, if there is one, may be in the increased velocity and longer life of the barrel. Accuracy may be a wash as well as ease of cleaning, IMO
http://i72.photobucket.com/albums/i186/ripley16/P7Chamberandbarrel.jpg

schmidtundve▀on
May 27, 2008, 08:05 AM
to usp9:

H&K P7?

atblis
May 27, 2008, 09:04 AM
Steyr GB

Rex B
May 27, 2008, 11:53 AM
American Arms Escort .380

NG VI
May 27, 2008, 12:05 PM
Quote:
Glock OEM barrels are 'hexagonal', same idea, similiar execution, H&K uses them, IMI/Magnum Research Baby Eagles, not sure who else uses them.


Glock .45's are octagonal, everything else is hexagonal, and both types are polygonal (I.E. hexagons and octagons are both polygons A.F.A.I.K.)! I like it, especially to make up for some lost velocity in compacts and subcompacts (I.E. kahr)! But it's not as big a factor for me in a full size.

Why do I have to open my mouth?

Anyway I wonder if anyone has any chrono data from two barrels of similair length with the same bullets? Maybe like a Glock 26/27/33 and a replacement non-polygynal barrel?

Shadow1198
May 27, 2008, 02:59 PM
That is most definitely a P7 barrel. :)

usp9
May 27, 2008, 08:44 PM
schmidtundve▀on,
to usp9:

H&K P7?

None other. :D

moooose102
May 28, 2008, 08:51 AM
so, if i am seeing correctly, instead of having grooves and lands, it is a barrel with, kind of flat or raised sections that are twisted. for lack of a better explanation. it almost looks a little like a microgroove barrel from marlin. so why do they want you to stay away from lead bullets? not enough engaugement?

usp9
May 28, 2008, 09:43 AM
so why do they want you to stay away from lead bullets? not enough engaugement?


The bullet to barrel fit is tighter than the more open lands and grooves, therefore the additional fouling from an unjacketed lead bullet increases the pressure over time. In other words, there is no place for the added material to go. Jacketed rounds leave far less material behind in the barrel. At what point it becomes an issue... I don't know.

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