Hammer forging is a bit different than buttoning a barrel, as you noted 404Bearlayer. As to accuracy, if properly rifled, they all possess better accuracy than a sporting rifle can show. Unles the sporting rifle needs deep grooves, they are all about par. Muzzleloading rifles of typical deep grooving for round balls, must be cut rifled.

Button rifling is the fastest and cheapest method of rifling, with hammer forging next in speed and cut rifling if a single point cutter is used, the slowest. The hammer mill rotates down the barrel as it hammers the steel onto the grooved mandrel. I'm not sure, but I think the short mandrel moves down the tube with the hammer mill as well. Otherwise, if might be impossible to remove. Not sure about that. Not sure about the twisting by Styer either, but was told the spirals are what is left after the mill runs down the outside in the hammer rifling process. If Styer does twist their barrels, this must be done prior to rifling. They then must stress relieve and anneal (perhaps one step) the blanks, then hammer forge, stress relieve, harden and temper. Perhaps.

CZ (BRNO) also hammer forges it's barrels. There are others. I was told Remington and now maybe Ruger as well was using hammer forged barrels now - but I don't know that for fact.

Any method will turn out a 1/2 MOA barrel on a sporting rifle stock & Mauser action. Some do, some don't. You generally get what you pay for in a barrel, but not always. Sometimes you'll find a gem for less than $200.00.