A lightweight 20 gauge is a joy to carry on long slogs in search of pheasants. But an effective load must balance acceptable recoil with sufficient pattern density and pellet energy. That convergence comes from 1 oz. of No. 6 shot with a muzzle velocity of about 1200 f.p.s.
Heavier payloads significantly boost recoil—a 3" shell firing 1¼ ozs. of shot results in 40 percent more. Also, additional velocity barely increases pellet energy. A No. 6 pellet, at 1330 f.p.s., carries only 0.3 ft-lb. more energy than one fired at 1200 f.p.s. Shooting larger shot is the only way to significantly increase pellet energy. An ounce of shot larger than No. 6s, though, carries an insufficient number of pellets to make a dense pattern at 40 yds.
This recipe’s 1 oz. of No. 6s, fired from the modified choke of a Beretta Whitewing over-under 20 gauge, printed 72 percent of its pellets in a 30" circle at 40 yds. Effective pattern diameter was about 30", with a lot of pellets clustered in the center. An improved-cylinder choke somewhat spread those pellets to enlarge the usable pattern diameter by a few inches.