Some are straight, some swirled.

IIRC, the threaded-on units are swirled.  This twist serves to tighten the unit onto the barrel.

The units installed with set-screws are not swirled, as no rotating force is either needed or desired.

Rummage around at www.entreprise.com/.  They list more different types of Vortex FS units than Smith Enterprises, the manufacturer.

Quoted: I doubt if the slanted prongs have any effect on tightening itself, I believe they're canted to give the prongs more surface area without adding length, kind of like sloped armor if you will.

From the manufacturer's web site, linked above:

"The Vortex incorporates a helix design essentially tightening itself when the weapon is fired and helps align exiting barrel gas to improve accuracy with all bullet types.

               - "Left Hand" slots for left hand threads

               - "Right Hand" slots for right hand threads

Flash suppression is not effected with straight slot muzzle devices."  

Quoted: Quoted: I've never seen a straight Vortex. Can't say that no more.  Old style with straight tines. www.hunt101.com/img/133095.JPG www.hunt101.com/img/133087.JPG

I have three (or four?) of these--I obtained them from Olympic Arms about ten years ago.  They have no name on them to indicate who the mfr. was.  The tines are definitely straight and there is NO flash whatsoever--none, even in complete darkness.  They are amazing.  I was at an AR15.com shoot where three of the four tines cracked and broke off of another guy's Vortex.  So far, no problem with any of mine.  

Ah, this was the thread I was replying to when my computer crashed last night.

OK, in the beginning there were straight prong Vortices, like the ones in Mongo's pic.  They are called Vortex because of the offsets on the INTERIOR of the tines. Look at Mongo's first pic for a clue. They worked really really well esp considering the competition available in the late 80's. The only problem they had was the couter rotation created by the propellant gasses eventualy loosened them. This was a bigger concern with the shorter barrels. Much Loc-Tite and torque was needed to keep them in place.

Smith Enterprises (SE) changed the design to incorporate helical flutes that off set the counter rotation. The helical flute model worked very very well and didn't come loose. They worked so well that SE couldn't keep up with demand. SE changed the design slightly to increase production. I've always called this design change the "straight flute" model because the cuts don't appear to curve around the circumference of the FS.

On this changed model the flutes are just cut at an angle to the bore line. The manufacturing change caused the prongs to be undercut at their base. There are the models that failed. SE claimed faulty heat treat on them but after checking several new ones against several known good ones the only difference found was the undercut tines.

Here's a close up from a recently posted pic showing the undercuts.


There was also a FS called the Brennan Nil-Flash. It looked somewhat like the Vortex but wasn't as aesthetic being just a cylinder with 4 internally curved prongs and straight flutes. Many of these were modified to look more like Vortices by shortening them and turning a groove into the ends. There was no way to modify the prongs so they still lack the triangular profiles used on the Vortex.

Quoted: Thanks!

All the credit goes to a member whose handle I can't remember. IIRC he is in Finland. I haven't been able to find the original thread anywhere despite it being one of "My Active Topics"

He had a beautifully mushroomed Vortex and was kind enough to post a detailed pic when I asked him.

You're welcome nonetheless.

Quoted: Quoted: Thanks! All the credit goes to a member whose handle I can't remember. IIRC he is in Finland. I haven't been able to find the original thread anywhere despite it being one of "My Active Topics" He had a beautifully mushroomed Vortex and was kind enough to post a detailed pic when I asked him. You're welcome nonetheless.

Tuukuo?

honest raf I can't remember. I've been adding credit to the photos I snag but I forgot his name.

Not even sure about the Finland part Bump, been talking to a lot of folks recently. Quite a few when I would have been better off sleeping. I'll turn it up again.

ETA, Found it, pic was by M4A2_LO73754 of FIN.

Tweak, tell me about the differences in the Phantom FS.  I have a 4-slot Phantom, with the wire-cutter cut-outs at the muzzle end.  How does that version stack uo against the Vortex and the other Phantom variants?

raf,

Forest arranged for me to test the protoypes of the new closed bottom Phantoms. I tested them against A1, A2, 3 prong, helical Vortex, and standard Phantom. I saw no difference between the saw tooth Phantoms and the ones with smooth ends. Test barrels were all 16" with ammo from the same SA battlepack.

All the Phantoms worked on par with the Vortx and far above the USGI FSs.