Late 580-series and newer w/ thick, tapered 5/8" barrel
Average of five 5-shot groups. Ammo: Federal 50 grain BTHP (jacketed hollow-point)
(std dev 0.48)
Comments: New barrel does show an improvement over the older skinnier barrel.
(std dev 0.45)
Comments: The Accu-strut has reduced group size by about 33%. Less dramatic change than with the old barrel, but still significant improvement. This is about the maximum improvement generally seen, in some cases change is much less. We're hearing of results anywhere in the range of 0-33% with the new thicker barrel.