Yes I religiously cannot focus up close anymore. .
Makes perfect sense... I'm in the same boat and have red dots mounted on three handguns, but all are with longer barrels.. It was the short barrel you have that caused the question..
The red dot takes sight radius out of the picture, so it doesn't really matter what the barrel length is other than velocity and how it feels in recoil. if anything, one can argue there's more advantage using the red dot on a short barrel to work around that short sight radius.
Short barrels can do just as well at distance as long barrels, especially when sight radius is not part of the equation.
