Is it a noticeable improvement in accuracy or primarily for reduction in effects of bullet weight/pressures?
And if it is an accuracy improvement, is it over the full spectrum of bullet weights?
edit: I know what Sadlak has to say. What is the real world scenario.
The piston is supposed too keep the barrel from flexing up and down from each venting of the gas cylinder and it does do that. However, I can tell you this, I've used my grooved TiN piston with everything from 125-185's weight bullets. Did I see a accuracy gain or improvement in my rifles from the bench or position.... Kind of sorta, but more importantly I didn't see it degrade either, what did change and was most feelable was the recoil impulse. The rifle has a softer straight push too the rear, instead of the normal bang and jab too the rear and the muzzle climbs up. Overall I would say it made the shooter more comfortable while the muzzle is pointed at the target still, my score's went up as the result of the better follow through.
That's the best I can describe the benefits/behavior of the grooved pistol, I know that recoil impulse is also subjective between different shooters, what I feel isn't the same as what you feel.
My piston is a early one from there 2nd run and its been in a few rifles over the years. Heavy, med, std. weight barrels and all behaved the same in each one the most dramatic difference for the better was with the GI contour barrel. So in a nut shell I say they work well.
