What is the "pentagon"?

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TROOPER
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What is the "pentagon"?

Post by TROOPER » Mon Jan 26, 2009 1:24 am

On my GLOCK OEM barrel it has the 6-digit gun ID, the GLOCK logo, and a small pentagon. What does that pentagon mean?
I read that it's douche to list your guns here, so I stopped that.

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Post by nomad » Mon Jan 26, 2009 2:53 am

I *think* that is the made in Austria proof seal/stamp.

If not, I'll be corrected in 1...2...3.....

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Diomed
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Post by Diomed » Mon Jan 26, 2009 3:49 am

I thought it meant it had polygonal rifling, but I really have no clue and am also curious.

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Jonas
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Post by Jonas » Wed Jan 28, 2009 4:15 am

Polygonal bore rifling

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TROOPER
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Post by TROOPER » Wed Jan 28, 2009 6:07 pm

Are you guessing it means "Polygonal"? Why don't some GLOCKs have it then?
I read that it's douche to list your guns here, so I stopped that.

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Post by Jonas » Wed Jan 28, 2009 9:37 pm

TROOPER wrote:Are you guessing it means "Polygonal"? Why don't some GLOCKs have it then?
I've never seen a Glock that didn't have a pentagon. I was under the impression that all Glocks have polygonal rifling.

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Beretta Steel
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Post by Beretta Steel » Fri Jan 30, 2009 2:16 am

You are correct it is the proof mark is for polygonal rifling (5 sides)
Not all glock have it because the 45's and 10mm don't have polygonal, rifling they have six sided rifling because the larger diameter bullet needs six sides to give the barrel more contact with the bullet. H&K is the same way

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Post by pneumagger » Fri Feb 06, 2009 4:00 pm

The rifline in my new G19 does not look "polygonal" in any sense like my desert eagle looked.
The glock almost looks like it has rounded ridges instead of lands/grooves.
My desert eagle barrel had what looked like a polygon with rounded-off corners.
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Post by TROOPER » Fri Feb 06, 2009 5:09 pm

pneumagger wrote:The rifline in my new G19 does not look "polygonal" in any sense like my desert eagle looked.
The glock almost looks like it has rounded ridges instead of lands/grooves.
My desert eagle barrel had what looked like a polygon with rounded-off corners.
I'm seeing the exact same thing in my own GLOCK barrel. It looks like distinct, smooth, hemispherical "speed-bumps" traveling the length of the barrel with a gentle spiral motion.

What confused me about this is that I'd expected the interior of the barrel to look significantly different from the LWD barrel which "allows the shooter to use lead-cast bullets". They look identical on the inside with the exception that the rifling is twists in the opposite direction.


I don't know what the Pentagon means, but it meaning "polygonal" doesn't feel like the right answer.
I read that it's douche to list your guns here, so I stopped that.

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spectac
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Post by spectac » Wed Apr 01, 2009 10:52 am

Way to go. now we got everyone looking down their barrels! :roll:
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Post by strobro32 » Wed Apr 01, 2009 6:56 pm

Hey, I just looked at my G19 barrel and it has lands and grooves, unlike the poly barrel in my Kahr. What's up with that? Is this typical of a G19?

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Post by studly do-right » Tue Apr 07, 2009 7:28 pm

Glock's polygonal siding is subtle. It's more rounded than others. That's why it won't look obviously plygonal. But if you collect a bullet fired from one it'll look much more flat sided than out of a non-polygonal sided barrel.
Beretta Steel wrote:You are correct it is the proof mark is for polygonal rifling (5 sides)
Not all glock have it because the 45's and 10mm don't have polygonal, rifling....
I think you mean "... they don't have pentagonal rifling...". They have hexagonal grooving. forgive me for getting technical, it's no big deal :wink:
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Re: What is the "pentagon"?

Post by JohnKSa » Wed Aug 23, 2017 2:30 am

You are correct it is the proof mark is for polygonal rifling (5 sides)
Not all glock have it because the 45's and 10mm don't have polygonal, rifling they have six sided rifling because the larger diameter bullet needs six sides to give the barrel more contact with the bullet. H&K is the same way
Pentagons, hexagons, and octagons are all types of polygons with different numbers of sides.

All Glock barrels have polygonal rifling but none of them have pentagonal (5-sided) rifling.

The polygonal rifling in Glock barrels is either hexagonal (6-sided) or octagonal (8-sided) rifling depending on the model/caliber.

Not all H&K pistols use polygonal rifling. I have one of the early H&K USP pistols and it has standard rifling.
Glock's polygonal siding is subtle. It's more rounded than others. That's why it won't look obviously plygonal. But if you collect a bullet fired from one it'll look much more flat sided than out of a non-polygonal sided barrel.
Correct. It's not simple to tell that it's polygonal from looking down the bore but you can tell either by looking at a fired bullet, or by looking at the profile of the rifling where it intersects the crown. The latter is especially telling when it is done side-by-side with a barrel with conventional rifling.

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Re: What is the "pentagon"?

Post by doubloon » Wed Aug 23, 2017 10:25 pm

JohnKSa wrote:... Pentagons, hexagons, and octagons are all types of polygons with different numbers of sides.
...
Dude!

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Re: What is the "pentagon"?

Post by JohnKSa » Wed Aug 23, 2017 11:11 pm

I looked at the age of the thread when I responded and debated just leaving it alone.

But the fact that I pulled it up in a search for information means that even though it's very old it's still visible and is still likely to be used as a resource by someone searching for information on the topic.

A big part of the value of any forum is the information contained therein. It's in every member's interest to try to insure that as much of that information is accurate as possible.

Besides, with only one post from this month in the handgun subforum, it's not like there's a big problem with people cluttering up the board with responses... :D

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