The grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling, a throwback to the earliest types of rifling, has become popular, especially in handguns.Polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land (the grooves are the spaces that are cut out, and the resulting ridges are. A. Slug weight. B. Powder and charge. C. Primer used, Fed 209A, CCI 209M etc. D. Velocity fps. E. Hull size 2 3/4 or 3 inch. The color coding looks good to the eyes but wonder what it would do leaving those colors in the barrels. Does any of you have the 20 gauge version and how good do they perform.