"In theory, practice and theory are the same, in practice they ain't." Yogi Berra.
In theory you should lose about 50-75 fps from 23 to 27 but I've seen instances where a particular shorter barreled gun would consistantly out perform a longer barreled one.
Without a chronograph best you can do is guess. Of Course even with a chronograph yor still guessing on what'll work.
