Well it further reduces the arm range which is a plus. The fire rate reduction isn't much of a big deal, but it reduces the clip size down to 3. As for the fire chance, it's minimal. 5 projectiles at 20% chance each has a probability of 3 fires per clip.
You'd think a 50% chance would be nice but then people'll start loading it in a gatling and.. dear god.
Welp, even more incentive to chemspray!