Polygonal rifling - what is this?

R

rock_jock

New member
Given the definition of a polygon being "a closed plane figure composed of three of more line segments", how is the rifling of a Glock polygonal? I look thru the barrel and, guess what? - It's round, just like every other handgun (it would be a little difficult to twist a bullet thru any true polygon). How does this rifling differ from other, more conventional rifling, and what are its advantages?

Thanks,
rock
 
If you look into the muzzle end of the barrel on a Glock, it will look octagonal instead of round with the sharp-edged lands and grooves like a traditional barrel.

Polygonal rifling provides a tighter seal around the bullet and reduced friction, generally resulting in less fouling and slightly higher muzzle velocity.
 
Take another look, Rex. It's definately not conventional lands and grooves (sort of concentric circles that are connectd in places), but a series of flats (sides of a polygon) that are twisted through the length of the barrel.

The polygonal rifling has less contact area with the bullet and there aren't any protrusions to wear significantly.
 
Uh, that's what I said, D6. It will look octagonal INSTEAD of round with sharp-edged lands and grooves like a traditional barrel.
 
Hold it. You lost me here.
1)The polygonal rifling provides a tighter seal yet has LESS contact with the bullet. Tighter yet less friction?
2)Polygonal rifling gets less fouling, yet Glock barrels, especially in .40 S&W, are said to be prone to fouling.
This doesn't make sense to me. I would think a tighter seal would have more friction.
 
I can't say on the more or less contact, but I think that the less fouling part comes from the fact that there are less small corners to hold fouling. The polygonal rifling, by definition doesn't creat the small corners that conventional land/grove rifling does.

I hope more people can rule in on the contact question. I can see where the polygonal rifling would create less friction, but it looks to me like the closer a bore is to a true circle, the more contact it would have with a bullet. Which would be the reason p. rifling would have less friction, less contact. OK, who's right here. I'm confused! -JHP
 
Standard rifling cuts into the bullet; hence fouling/friction from extra work.
Poly rifling molds the bullet to the barrel; better gas seal, less friction (no cutting work).
 
Draw an octagonal shape on a piece of paper, and you will see there are 8 22 1/2 degree corners, and 8 flats that the bullet is conforming to.

Draw a circle roughly the same size as your octagon, then draw in 6 lands like a typical conventional pistol barrel has. you will see there are 24 corners of approximately 90 degrees, 18 flat, and 12 curved surfaces the bullet has to conform to to create a perfect seal. The surface area contacting the bullet is much greater in this shape as well, creating more friction.
 
Right or wrong Rex, I don't know... but your impressive mathematical equations need to be recalculated with a Polygon (6 sides), not an Octagon. ;)
 
Not trying to be a know-it-all Onslaught, but the prefix poly means many. A ploygon can also be a pentagon, hexagon, octagon, etc., etc. The hexagon is a six sided figure. ;)

All the polygonal barrels that I've seen were octagonal in cross section.
 
Right or wrong Rex, I don't know... but your impressive mathematical equations need to be recalculated with a Polygon (6 sides), not an Octagon
Click to expand...

Uh, a polygon is a not restricted to 6 sides, thats a hexagon. Polygon just means "many sides", and Rex apparently has a .45 Glock, since they have 8 flats in their barrels, where the 9mm and .40S&W have 6.
 
Bite your tounge BB, I have a .45 H&K USP w/ polygonal rifling. I HAD a .45 glock that I was very unhappy with. ;)

How do you reply w/quote in the new TFL format anyway?
 
Polygonal barrels don't have conventional lands and grooves, but spin the bullet by causing it to be pushed thorough a flat sided tube that is twisted.

As the tube is flat sided, more of the bullet contacts a flat surface in the barrel than is the case with conventional barrels. Because of this, leading of the barrel occurs much more rapidly than with conventional barrels -- hence the warning not to shoot lead in Glocks, H&Ks, etc.

When my son went through Police training, he used my Glock 17. they provided the ammo -- with lead bullets. We cleaned it thoroughly each night after range sessions, and there was substantial lead build up.

It functioned flawlessly and accurately throughout the class -- which was not the case for the worn-out S&W semiautos everyone else had to use. (He had the highest scores, at least in part due to a better functioning weapon. Had the S&Ws -- the schools guns -- been in better shape, it might've been a different story.)
 
Now lets spice the thread up some by asking the question - Which is more accurate conventional or poly rifling and why?
 
This is great information - one of the reasons I like TFL, plus we have an opportunity for a little debate.

I did take another look at the muzzle, but I could not make out a distinct polygon, probably because the crown smooths the end out (or, the crown is smoothed out). Anyway, what you are saying is that if I cut a Glock barrel in half, the cross-sectional profile would appear as a polygon, with flat sides? If so, the bullet is not making contact with the corners, but I understand what you are saying about the bullet making greater contact with the barrel as a whole, i.e., more surface area to contact. This would also seem to make polygonal rifling more accurate, unless, of course, conventional rifling would "hold" the bullet better by cutting into it, thus providing greater stability in the barrel and a more stable flight path (better accuracy).
 
Im so confused!!!!!!



STILL !!!!



I guess ill have to buy a glock and study that barrel.



P.S. Ive been looking for a good reason to buy a glock. Thanks guys!


Tim : )
 
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