Heckler Koch, and others have used polygonal rifling (no rifling grooves,just flat sides like the inside of a hexbolt head)in barrels claiming less fouling and 5% increase in velocity over normal rifling. Some custom tactical rifle makers in the US use these barrels also claiming increase in velocities.Ie: 180/300mag@2960 in normal barrel,3100 in polygonal barrel.
Does anyone have info on these tubes?

If we’re talking about the same thing, your description isn’t accurate. They don’t have flat sides.

This kind of rifling does have the equivalent of “lands and groovesâ€...but there is no distinct transition between them like on traditional types. They are sometimes called “hills and valleys.â€

http://yarchive.net/gun/barrel/polygonal_rifling.html

http://www.streetpro.com/usp/uspfaq.html look at the first block of questions"what is polygonal rifling.."

Lothar Walther makes these barrels. Only two calibers listed in rifles .223 and 30 cal. HK also uses these on some of there rifles, the PSG1 comes to mind.

I thought the advantage of these was they don't wear out as fast, which is why you see them in military rifles.

quote:

Originally posted by Woodjack:
Heckler Koch, and others have used polygonal rifling (no rifling grooves,just flat sides like the inside of a hexbolt head)in barrels claiming less fouling and 5% increase in velocity over normal rifling. Some custom tactical rifle makers in the US use these barrels also claiming increase in velocities.Ie: 180/300mag@2960 in normal barrel,3100 in polygonal barrel.
Does anyone have info on these tubes?

You description is accurate---at least as pertaining to Heckler and Koch polygonal rifling: the rifling profile consists of segments of flats comprising the 360 degrees of radius inside the bore. I've owned four or five HK 630s, a couple of HK 300s and one SL6 over the years. All were very accurate. The 630s would group close to a dime at 100 yards with the right ammo. Of course some of that no doubt had to do with the delayed roller locked action.
I believe Schneider barrels make a polygonal rifled barrel. I think David Tubb swears by their barrels. I dona't know who else makes them. Lothar Walther offers them in .22, 9mm and .30 caliber.


Jordan

Pac-Nor lists them too.

I have had some rifles with polygonal rifling over the years, and still have 3 or 4.

There are several claimed advantages to that style of rifling, but it is worth noting that EVERY different kind of rifling has some claimed advantages over whatever it is competing with.

One of the claimed advantages of polygonal rifling is that it does NOT reduce the diameter of the bullet. Although the bullet IS squeezed into a different shape, the total area of the bore is the same as the nominal cross-sectional area of the bullet (assuming a bullet that fits correctly is used in the first place). This also means that the bullet does not develop any rearward "fins" from the rifling pushing its way through the bullet as the bullet enters the bore. That may be true, but with the accuracy of the many benchrest barrels which do not have polygonal rifling, I am not sure how much (if any) of a benefit it is in shoulder-fired weaponry.

And actually, I am not sure all of the claimants of advantages are really talking about the same kind of bore to start with...

Some use a bore of a particular shape, where the bore itself tists for the entire length of the barrel. That is, it may be an oval shape for instance, but the oval twists as a whole on the way down the bore. Others are talking about rifling that has a series of overlapping ovals which twine around each other sort of akin to "braiding" as they go down the bore.

At any rate, my polygonal rifled barrels do not seem to shoot, on the average, any better or any worse than any of either my cut-rifled or button-rifled, or hammer-forged barrels of other bore designs. One polygonally-rifled .308 of mine is remarkably accurate with 190 gr. Hornady rebated boat-tail match bullets at slow velocity and low pressure, but on the other hand, it is remarkably inaccurate with anything else.

Unlike some things I have read in print, the polygonally rifled barrels I have seem to shoot cast lead bullets quite as well as any other kind of rifling does, with no particular leading or inaccuracy disadvantages. But, I suspect those negative reports about shooting cast bullets in polygonal rifling occur at least mainly because many cast bullet shooters out there simply do not understand the whole concept of bullet to chamber-throat fit, nor how important gas-cutting is as a contributor to leading, regardless of bullet temper.

quote:

But, I suspect those negative reports about shooting cast bullets in polygonal rifling occur at least mainly because many cast bullet shooters out there simply do not understand the whole concept of bullet to chamber-throat fit, nor how important gas-cutting is as a contributor to leading, regardless of bullet temper.

AC,

I was wondering about the actual source of the Glock lead bullet kabooms, so I asked some guys who shoot Glocks and Know About such. Their reply was that the Glock barrels are formed in such a way that they build up lead at the firing end, and sooner or later enough lead is present that the pistol fires without the action locked. The result is a kaboom.

One shooter claims 40,000 lead bullets through his Glock by consistently cleaning and removing lead build-up. The others just don't shoot lead.

The same condition would be hard to develop in a rifle I expect.

jim

quote:

Originally posted by HunterJim:


AC,

I was wondering about the actual source of the Glock lead bullet kabooms, so I asked some guys who shoot Glocks and Know About such. Their reply was that the Glock barrels are formed in such a way that they build up lead at the firing end, and sooner or later enough lead is present that the pistol fires without the action locked.

One shooter claims 40,000 lead bullets through his Glock by consistently cleaning and removing lead build-up. The others just don't shoot lead.


jim

Yes the whole Glock/lead bullet thing is an interesting issue. Personally, I don't believe the way the barrel is built has a darned thing to do with it.

I suspect it is more a question of bullet size & shape. It IS quite feasible that some conventional bullets, particularly wadcutter or semi-wadcutter designs have a large enough shoulder that lead is sheared from the bullet(s) as they are seated in the chamber prior to firing.

But, that has nothing to do with the way the barrel is built, just whether the shooter takes the pains and has the knowledge to use the right diameter, temper and shape of bullet(s) to atart with.

I certainly am NOT a Glock expert. I do carry a Glock every day of my life (a Model 20, 10 m/m), but I don't use lead in it. Courts tend to get iffy if you shoot a perp with a handload. So, I carry mine stuffed with 16 Black Talons. (Not that I'm liable to ever have to shoot anyone, I hope! I've been retired 14 years...)

At the same time, I do act as Range Officer every year at a Glock regional match for the GSSF(Glock Shooting Sports Foundation), and many members of our club shoot Glocks weekly in various of our club activities, including a match once per month. Quite a few of them use lead bullets in their Glocks. Some others of them get the "horrors" at the very thought of lead in their pistols. Some of the lead shooters I've talked with don't go to any extra trouble cleaning their Glocks either, or so they say.

So, none of that adds up to evidence either way for me. I have seen Glocks blow up with handloads, but none of those handloads were lead bullet loads. In each instance, the load was simply too hot, considering the relatively unsupported base of the cartridge case in the standard Glock chamber, and the "Kaboom" was a failure of the cartridge case at the base end.

What I feel I am left with is having to consider the engineering details and mechanical pinciples of fitting bullets to ANY firearm. Myself, I have been unable to find any mechanical or engineering reason that a PROPERLY shaped and sized bullet should fail in ANY kind of rifling or brand of barrel or chamber.

If I wanted to shoot lead bullets through a Glock, I would start with LOW pressures, experiment with different shapes and diameters of bullets so that no shearing occured as rounds were chambered. (I'd carefully check the chamber throat after chambering and after firing each round while testing my loads, until I was sure no such shearing or leading was occuring.) I would also be VERY careful to use a taper crimp rather than any amount of roll crimp, to assure my rounds maintained proper headspace when chambered.

And, I might blow myself up, but I don't think so....