Air flowing across a spinning cylinder creates a force at 90 degrees to the direction of the air flow.... called Magnus effect. The more texture (to a point), the more force. This is the vertical change in a projectile in a cross wind. This same texture creates drag which allows the wind to act directly on the projectile. A cut rifled barrel imparts a fairly definite and sharp texture to the pellet where the ST barrel or the Walther poly impart no sharp imprints so there is less texture for less pronounced effect. It's been noted by some that the cut rifled barrel is more accurate in still conditions and shorter ranges but the ST and poly are generally better for wind and longer ranges. Each barrel is it's own entity though so I don't know if you could call it an absolute.
Bob
^This is the answer, and why we now see polygonal barrels starting to dominate in places like Extreme Benchrest. (note Daystate now uses polygonal barrels too after getting their ass kicked several years running by FX's original Smooth Twist barrels which are, quite frankly, a bit of a manufacturing hack that really end up acting as kind poorly performing polygonal gain-twist barrels)
There is no real debate that polygonal barrels are, hypothetically all else being equal, are superior to your typical sharp cut land and groove rifled barrels. They also tend to produce better gas seal. The problem here though, the reason for all the disclaimers of "hypothetically all else being equal" is that there is a lot more to manufacturing a good barrel than the rifling. Take the firearms industry for example: Bartlein barrels are currently dominating long range shooting, and they use single point cut land and groove rifling. Why? I maintain it is because of the care with which they make their barrels.
I must confess, I'm rather surprised to hear that an Umarex Gauntlet was a contender here. A lapped Lothar Walther out of a RAW or Daystate I could understand someone making the argument, although the best shooters at the time suggest that still is incorrect again look at EBR, but an entry level Gauntlet? To be brutally honest, sounds denial to me. It is a big river with crocodiles and a nice view of the pyramids. Precision shooters don't generally quantify barrels in terms of "just as accurate," because they've shot the groups and done the math and can tell you on average how much more or less accurate something is, and there is ALWAYS a difference.
Polygon barrels dominate in places ? I don't think so .
The FACT is, except the Extreme benchrest, land & groove barrels dominate in short-range low power airgun shooting competitions all over the world
The FACT is conventionally rifled barrels dominate almost all the firearm competitions all over the world
The FACT is almost all the snipers use Land & groove barrels all over the world.
Why do polygon barrels dominate in EB ? it's just because FX focuses on high power airgun platform and they do a good job. It's not because FX use the polygon barrels. Daystate will not dominate in EB even if they use polygon barrels. In other words, Fx will still dominate in EB, even if they use land&groove barrels.
Fx will never win the Nobel prize in the barrel making industry. The inventor of polygon barrels didn't win a nobel pirze. Polygon was not, is not ,will never be a high-tech stuff.
All the major barrel makers in the world with far more capital expense , far more talents, far more patents than FX ，mainly produce conventional land&groove barrels.
I have actually been following the precision rifle world for some time now, at least reasonably closely, for both gunpowder and air. If you keep an eye on Cal Zant's work for example, you'll note that almost everyone uses single point cut rifled barrels. The why there is important though, and this is where I think you and I start to diverge. I'm talking more about the theory side of things, and I at least believe you're talking more the practice side of things. So lets talk quickly about the why of that. There is a lot more time and money in the firearms industry, so I'll use that as the example.
Bartlein, Kreiger, K&P, you name it, the brands that dominate PRS are all land and groove single point cut rifling. Why, especially when polygonal is better? (and remember, it is better not just in terms of ballistics which is what we're "debating" here, it is demonstrably better in terms of other things including muzzle velocity due to gas seal, reduced fouling, increased barrel life which is extremely important in these high throat erosion precision barrels which can have lifespans of less than 1000 rounds, etc) The answer isn't in how they perform, it is in how they're manufactured. A single point cut rifled barrel is made from a bar stock which is first gundrilled, and then (as implied by the name) cut at a single point in the bore by a CNC machine. This allows any rifling pattern, any twist rate, and even complex architectures such as gain twist rates to be trivially manufactured. For guys who precision shoot in the firearms industry, this is great for them because they're constantly experimenting to develop their own loads, chambers, and barrels to get the best performance possible. Now compare this to how you make a polygonal barrel. You have two choices: button rifling or cold hammer forging. Both rifling buttons and CHF mandrels are comparatively expensive pieces of tooling, not to mention the CHF machine itself is incredibly expensive. CHF results in demonstrably superior barrels, however the cost means only larger manufacturers can afford to do it. While it is possible to make a gain twist rifled barrel via that technology, doing so is even more expensive as it requires a full mandrel for that specific barrel. Button rifling can only cut a single twist rate (rare exceptions apply), and would require quite a special button to put a choke on a barrel as well. And again, in both these cases, the startup cost for a twist rate in a given caliber is high, much higher than cut rifling, which is why cut rifling is much more common and dominates even at the high end of precision rifle shooting.
Similar reasons as this apply to other such as airguns, as we tend to get the cast-offs of the firearms industry. The observable difference in performance is quite small, particularly at short range low power competitions, so manufacturers are unlikely to invest in polygonal. Also things like barrel life are so much higher with airguns many people consider them to be essentially "unlimited" or implicitly do anyway as they don't even consider it, so one of the major advantages of polygonal is scrubbed away right there. Another is we don't shoot jacketed ammo with airguns, so scrub away another advantage of polygonal there as well.
Snipers the world over use whatever the military issues to them, and some of those guns are land and groove cut and some are polygonal (such as the PSG-1 or LaRue), and the same holds true for issue weapons as a matter of fact. We can debate the relevance of "what the military uses" but generally speaking I think of what the military uses as being dictated at best by what fulfills the requirement cheapest and at worst what company bought off the right politicians. The US military is still using .308 as a long range precision rifle cartridge (not exclusively, granted), a decision which wasn't great even when it was made. Far from optimized technology.
To be clear, I'm not making an argument for or against FX in all of this. Their original smooth twist barrels, in my opinion, were a clever manufacturing hack to bring barrel manufacturing in-house for even cheaper than a single point cut rifling machine/s in order to keep up with production. A mostly smooth barrel with rifling only the last couple inches is NOT the optimal way to spin a projectile, but it is a credit to their ingenuity that they got it to work. The same can be said of their current STX barrel liner system. It is a clever manufacturing workaround, but it is not the optimal way to apply the technology. To my knowledge Daystate and RAW are now using proper polygonal barrels turned from a larger OD blank and made via whatever technology LW is using, which is how you'd want it done. I at least suspect this was spurred on by FX's success with the technology, but I highly doubt they'd do it if they didn't see better results from it.
EBR was simply an example because it is one of the most prestigious high power airgun competitions I'm aware of, and draws some of the biggest players in the game from around the world to come compete. So it is a sandbox in which the latest technology can play, and while such competitions are also skill based meaning it isn't the end all, I do think it is worthwhile to keep an eye on the results and use that as an indicator of what is working.
Not FX, or anyone, would win a Nobel Prize for polygonal rifling because the first Nobel prizes were awarded in 1901, at which time polygonal rifling technology was centuries old. It is FAR from a new technology.
I hope that clears everything up. I'm not some FX ***** hanging on Ted Bier's every word. I'm just an engineer, with some vague background in the tactical industry. Plenty of competitions have been, and will continue to be, won with land and groove rifling, but there are still definitive advantages to polygonal rifling OF EQUAL QUALITY MANUFACTURE AND OTHERWISE IDENTICAL SYSTEMS to land and groove rifling. Again I put that disclaimer in because the differences are NOT massive, and you have to go looking for them, but when you're looking for an advantage of say .02 miliradians averaged over dozens of groups, you're really going to have to go looking. Advantages which are huge and obvious aren't called advantages anymore because everyone has adopted them and is using them.
And because I'm just some random dude from the internet, I've got a couple sources, some general, some anecdotal, you can peruse if you're interested.
https://en.wikipedia.org/wiki/Polygonal_rifling https://bearingarms.com/ccantrell/2010/06/08/barrels-and-bullets-conventional-versus-polygonal-rifling/ http://www.ballisticsbytheinch.com/rifling.html https://www.thefirearmblog.com/blog/2016/06/10/the-more-you-know-polygonal-rifling/ http://www.majorpandemic.com/2012/07/ultimate-1022-shootout-test.html I hope all this is helpful to someone.
very good explanation. I concur. 
