Have one on one of my 220 Swifts and just for S&G's bought one of these to test it out. Had loaded up 200 of its pet loads that were consistantly printing sub 1/2" groups.
Took it to range and started out with a fresh cleaned barrel. Fired a fouling round.
Started with it 4 inches from muzzle. Fired 5 shots, spaced one minute apart and let stand 10 minutes. Cleaned barrel. Swabbed with patch n solvent, 10 strokes with nylon brush from breach with bore guide. Dry patch, fouling round, start again.

Long story short, fired all rounds, spent all day, back yard range. Come to find out that 90% of the groups didn't change that much till I got with in 1-1/2" of forearm and the groups went nearly sub 1/4". Ran out of ammo by this time. Loaded more ammo, same everything across the board, back out same day.
Went up against forearm, rounds got wild. Backed out to just at 1" and groups went back tight again. like just before. Left it at just about 1 to 1-1/2" and it drives nails. My personal experience.