27.5 is way too fast... the gun doesn't actually shoot at 27.5, it is probably shooting at 1/3 of that speed with some skiping, or 9.2 shots per second.
For example, if the cap is around 8 sps... if you fire at 24, the game might only be "Seeing" every third or so shot since you are shooting way too fast for it to detect. Really it's only going to see about 9 sps, but you'll also have skipping/lagging badly since you are shooting way too fast. It might work o.k. for SOME people depending on a lot of variables, but for smooth firing for the masses, you should really be down around 10 sps or less depending on the game.