+P ammo requires a four-inch minimum barrel to burn the extra powder. Therefore, in a two-inch barrel the extra powder is burned after the bullet leaves the barrel creating more recoil and making it harder to come back to target.
Bear in mind that I last reloaded pistol ammunition was in the early 80's.
I remember different powders having different burn rates, the larger rifle powders had less surface area on each piece of powder, which weighed more per piece than the smaller, finer pistol powders. I'm using "piece" instead of "grain" to avoid confusion with the word "grain" denoting the weight of the powder. It's clumsier but I am trying for cliarty.
From my ancient reading back in the 70's the finer powder burned faster allowing it to burn away in the time it took for a bullet to travel a pistol barrel's length. Rifle powders burned slower to keep that exploding gas behind a bullet traveling 16" or more of rifle barrel.
This is what seems to me to be a knock on guns like the Draco and the various AR pistols, unless you're reloading, you're using commercial rifle bullets designed to continue burning for as long as it would take a bullet to travel that first 16" resulting in a big fireball at the muzzle of wasted powder.
I don't know if the +P ammo factory ammo just uses a dab more powder than the standard rounds or if they use a different powder altogether, but it seems to me that the burn rate would be, whichever is used, would give a big fireball of wasted powder out of a 2" barrel when they're engineered to potentially travel a 6" barrel.
I used to load a 125 gr JHP round on top of 7 grains of Unique powder for my .357 and it was a healthy round and that Unique powder was almost like dust.
