Home Forums Hunting & Shooting Ask The Gunwriters polygonal rifling any advantages?

Wondering what it provides over ordinary rifling, if any?

The poly rifles I have seem to be just a touch faster than traditional rifling methods. They're also smoother when cleaning. However, I don't see enough of an "advantage" to seek them out, exclusively.

Faster, and smoother to clean sounds good. Do they seem as accurate as traditional rifling?

OTOH, you can't use cast bullets in them without excessive leading.

Denton, not doubting you as there are many on the fire that are far more knowledgeable than I, but when I was in re-qualification module
with the local sheriffs office the Glock factory rep was there. He expressly said NOT to use cast bullets as they'll foul the barrel and make
it explode due to excessive leading.


Just curious - Anyone else know about using cast in polygonal barrels ?

I think we are in violent agreement. You can't use lead bullets in polygonal barrels.

The Confederacy had a fine rifle with polygonal rifling, and found excessive leading back then. So it isn't a recently discovered problem.

Maybe uncoated lead bullets are an issue, but I've put thousands of coated lead bullets through a G17 without issue, and seen other Glocks that have had had more coated bullets through them than mine, again without issue.

I know a number of people who have used lead bullets in factory Glock barrels without problems. However, I think it would be wise to clean the barrel thoroughly on a regular basis if you're using lead bullets. It might be more of a problem in a rifle since pressures are generally much higher.

A primary cause of leading is stripping at land engagement. Poly barrels tend to exacerbate this, due to the rounded and shallow nature of the rifling.

A rock hard, groove diameter checked bullet would easily get around any such issue. As mentioned, coated stuff can too. It's pretty simple: make a bullet that doesn't strip at engagement or use the paint/poly jacket.
Unfortunately, most bulk cast bullets can't always be counted on not to strip, at the very least most are sold with "lube" that promotes leading even in traditionally rifled bores.


I think the primary use for polygonal rifling is cost related.

Whitworth

Dont tell Whitworth....


Sorry, can't get the link up there. Anyway, the Whitworth rifle wasn't prone to lead fouling, it was more prone to black powder fouling to maintain its precision and ease of loading. It used FITTED, hardened for the era, polygonal bullets and required more field maintenance than undersized patched balls, for obvious reasons.


It was also miles ahead of its competition when it came to accuracy.

Shilen offered barrels with polygon rifling for a while in the mid to late 70's, didn't last long as it must not have caught on.

This link should work:


Whitworth rifle

YouTuber capandball has scads of videos about shooting rifles of that era, originals and good repros. Hunts and shoots in competition. He's got a piece or two on the Whitworth, a Pedersoli, I believe. Watching those can be expensive; I ended up with a Parker Hale 1858.

I think those are actually hexagonal rather than polygonal though. I've seen reports of good results with regular round bullets like the Lyman 500gr .457 though.

If a jacketed rifle bullet was seated in the case with a non-concentric runout problem, could poly rifling shoot it more accurately than land and groove rifling?

although handguns.........my two H&K 40's are very accurate with poly rifling

Not sure about the poly rifling but Shilen still offers what they call "ratchet rifling" which is closer to the 5R or radius rifling than to poly.

I have heard poly barrels can last longer but have not seen any valid tests on this. It makes sense as there are less acute angles to get rounded off but since most barrels it is the throat that goes it may make no difference. David Tubb shot them a couple of seasons but he doesn't stick with any barrel for very long. He could also win matches shooting a rusty galvanized pipe.

No. That is absolutely 100% wrong. That's a common internet myth repeated by people who have no experience with it. Continuing to repeat this does a disservice to the community and makes everyone who believes it dumber.

Thousands of Glock and other polygonal bore shooters use lead bullets successfully on a regular basis, both wax lubed cast and coated styles. The requirements for using lead in polygonal bores is not much different than traditional land and groove rifling, and in most cases anything that leads a polygonal bore will also lead in traditional rifling. The exception is very soft swaged lead bullets which are too soft to grip the polygonal rifling well; that results in loss of gas seal and gas cutting of the bullet, which causes leading. The "no lead in polygonal rifling" rumor started because of those soft swaged bullets, but they aren't in common use any more, and most cast bullets are hard enough that it's not an issue. Coating does not get us around the soft bullet issue either although it can reduce leading.

I shoot about 6,000-8,000 rounds of cast bullets through polygonal Glock (and now Tanfoglio too) barrels with zero issues. I shoot coated bullets now, but did the same with wax lubed cast bullets for a long time before coating. In my experience, the high quality finish of most polygonal bores is actually better for lead than common traditionally rifled barrels.

Here's a 9mm coated bullet recovered from one of my Glock barrels. There is zero sign of leading or coating failure on that bullet, and it's a pretty typical representation of what I recover.

Yes in my experience; of course it depends on barrel quality same as with any other rifling type. Black Hole Weaponry uses Caudle polygonal rifling for their rifle barrels and are known for good accuracy; I only have one (a .243 LBC) and built another in 6.5 Creed for a buddy, both of those definitely live up to match grade accuracy expectations.

Tanfoglio uses polygonal bores (I'm told they are Lothar Walther) for their match barrels, and those are known for exceptional accuracy, mine is no exception there.

A lot of people complain about Glock accuracy, but that's more about the trigger being harder to manage and looser tolerances; in competition shooter circles switching to an aftermarket barrels is generally considered an insignificant change in accuracy and sometimes worse. My own experience with a bunch of aftermarket Glock barrels is that most of them don't shoot any better than the factory Glock bores, with the occasional exception of a Glock barrel that doesn't lock up consistently.

HK uses polygonal bores in a lot of their guns too, with generally good accuracy results.

There is a lot of bad information out there about polygonal bores, mostly because people are just unfamiliar with them (and the common attitude that "what I'm familiar with must be best"). If there are any downsides to a polygonal bore, accuracy isn't one of them.

hexagonal is polygonal. Hex meaning "six", poly meaning "multiple" or "many".

A polygon has multiple sides. A hexagon has exactly 6 sides, octagon has 8 sides, etc, both are polygons.

I'm in Yondering's camp on this. Polygonal rifling was the norm in the early period of gun making, notably by the Brits and others in Europe. They shot lead quite well back in the day. Keep in mind that "poly" means whatever the barrel maker wanted it to mean and the dimensions where his to craft. Also know that many shooters from that era used paper patch which inserts a very different metric in the game so far as leading/obturation/precision goes. 6 flats, paper patched pure lead? Hell ya!