Take with a grain of salt REDCELL, about the 2" groups at 25yds.
It is done with finely tune pistols, with the correct reloads, by trained shooters.
I will do it with my S&W 617 .22.
With my new Tanfoglio 9mm., I am still getting used to it, am still loading up different types of reloads, and I am shooting 6" groups at best.
I'm a good shot, and haven't shot enough rounds to figure out if the 6" groups at 25yds are because of me, my reloads, the gun, or a combination of the three.
I will eventually get down to small groups this summer when it warms up here in Minnesota.
With the type of shooting that you are doing, don't worry about it.
Just have fun, and figure if a big fat guy comes at you, he is toast.