Have heard good things about polygonal rifling but can't find alot of info/tests on it. Wondered if anyone here could tell me what the downside of it is as so far I haven't found one.

Thanks in advance.

wildcat---

If you're talking about the stuff Shilen used to do......I tried one barrel on a 40 XBBR rifle that shot in the .2s in competetion....it changed it to .4s, so I swapped back. That was 1974 I think. The groups were round, but big.

One of the main problems with the DGA barrels, as they were called, was that the rifling wouldn't turn the brush so they were often not cleaned well. I used one on a cast bulley rifle and it worked real well.
The current "ratchet rifled" barrel by Shilen is also sort of a polygon and seems better.
In the end the best that can be said is they work as well as conventional rifling. Usually. Regards, Bill.

Wildcat,

I had posted a question onpolygonal vs conventional rifling some months ago and if you do a search on this forum you will find it. There was a particularly interesting reply from the president of Lothar Walther who make both cut and polygonal rifled barrels about a very slight velocity increase of about 3 % with polygonal rifling with other attributes remaining the same.

If you do build a rifle with a polygonal barrel (LW make them in 223, 308 and 30-06) do post the results here.

Good shooting!

Didn't Heckler & Koch use those at one time? Was thinking they used poly barrels on the HK91's and 93's, but that was some time back. Seemed to me that they were very accurate for semi-autos.

This is from a vague memory, so don't jump all over me if it is wrong, but doesn't or didn't Glock use polygonal rifling in their pistols? If it isn't Glock it is some other well known maker, such as Sig.

Gatogordo,

So now your memory is fading. Darn shame to have both of those things quit working. Yes, you are correct about Glock. They all have the polygonal rifling in their pistols.

Kahr arms also use polygonal rifling on their pistols.

Some runs of the HK assault rifles and pistols where also made with Poly. I believe manufactering dates where from the early 80s to about 92 for the poly'd USPs.
Polygon rifling produces a tighter gas seal with less bullet deformation hence the 3~5% increase in velocity.

I have a HK/91 with polygonal rifling & it's very accurate & seams easier to clean.

Both Glock and H&K use poly groove barrels in ther products. It works better with high pressure cartridges as the bullet has less friction. Cleans easier with a tight brush too. I am not too sure how they stack up against cut grooves for target barrels, but H&K's PSG-1 also has poly grooving and it is legendary for it's accuracy for a semi-auto rifle.

That must count for something, eh?

My two cents,

Eric

I copy-pasted the following from Lothar Walther's website :

"Urspr�nglich kommt diese Art des Laufprofils aus der Wehrtechnik, wo einer hohen Lebensdauer und einfachen Reinigung ein hoher Stellenwert beigemessen wird. Diese Vorteile werden mit Polygonl�ufen von Lothar Walther auch f�r Sport- und Jagdwaffen verf�gbar. Was die Schu�pr�zision der L�ufe mit Polygonprofil angeht, mu� man heute kaum noch Abstriche im Vergleich zum Standardprofil in Kauf nehmen."

Loosely translated, it says that this technique in bore profile emerged from military technology, where longer barrel life and simplified maintenance were highly prized. Those qualities are also found in Lothar Walther polygon bbls. for sporting and hunting firearms. In terms of accuracy, today's polygon bbls. hardly demonstrate any inferiority when compared to standard rifling.

Personnally, I'll stick to conventional rifling, broached or button-rifled...