Listen guys..... FX rifles are GREAT. The concept for their smooth twist barrel design is revolutionary and ingenious. But other than the barrel, they're using the same physics to send that slug downrange that you are. Regulated air, valve, hammer, spring, etc.... But once you understand WHY they are so accurate, the light bulb in your head goes off, and you think to yourself, "Well hell..... If a properly sealed barrel works so well for FX, then it should work for my rifled LW barrel as well." And you would be correct in this statement. According to the Berger TW calculator, the TJ's 36.2gr .250 slug should have max stability using the slower 1:17.7 twist of the LW barrel, even when shot at 900 fps. But the calculator doesn't take into effect the issue of the slug not fully sealing inside of the barrel grooves, and the destabilizing that takes place from the escaping air, and/or the slug slightly canting inside of the barrel due to the gapping. That's why a properly sealed barrel is so important. It forces the slug to stay perfectly concentric.
Now I will admit, not all barrels are made equal. L-W barrels are mass produced. Their attention to detail lacks compared to say a CZ or Russian Made, or TJ's barrel. But it's nothing that can't be fixed with a fire lap, or bore lap to smooth the inside of that thing to a mirror finish, and level out any high spots. A clean barrel will have less lead fouling. Also, twist is indeed important. The .22 LW barrel with a twist of 1:17.7 is significantly less stable than a 1:16 twist shooting the same projectile at the same velocity.
I'm convinced FX is fully aware of why their smooth twist barrels out perform rifled barrels. But from their perspective, can you blame them for not disclosing this info? They manufacture very high end, and very expensive rifles. They dominate bench rest competitions. They're using the same projectiles as the rifled barrels. They're using the same methods to propel it down range. The ONLY difference is the barrel. And when you understand the physics of the barrel, and why the slugs MUST be slightly larger than the inner barrel diameter, then the epiphany moment happens....
I suggest you guys do some R&D. Maybe I'll post a thread about powder coating small caliber slugs. Then you guys can coat your own, get them to seal inside your barrels, and watch what happens. If we can PROVE what we're saying is true, then the slug manufacturers might start producing .22 slugs in .221 or .222, and .25 slugs in .253 or .254.
Forgot to mention.... Another cool thing about powder coating slugs is there are some CRAZY colors of powder out there. Chartreuse, fluorescent, etc.... Colors that are HIGHLY VISIBLE on the color spectrum. Colors that you can actually track the trajectory of the slug with your naked eye as you watch it through your scope. You can even buy glow powders (strontium illuminate) and mix it in with your powder coating powder. It only takes a tiny bit. But if you get a cheap UV light, you can charge the slug before you fire it at night or in low light conditions. You essentially make a "tracer" round. But that's a whole other subject for a whole other thread. Like I said earlier, a clean barrel with have way less lead fouling. A clean barrel using powder coated slugs will have ZERO lead fouling. That's why even though Stephens AVS slugs already concentrically fit my .25 barrel, I powder coat them with a very thin layer anyways.