Hi I have a LAN Gaming event that I host every month.
We had 3 unmanaged switches with 60 PC's connected to them & the network was stable.
We have now added a 4th unmanaged switch and the ping rate in COD4 is over 300?
A managed switch may or may not make a difference. How do you have you switches set up? Are they daisy chained - i.e. one switch into the next switch, followed by the next switch, ans so on? This can cause problems. You would be better off connecting 3 switches into the first switch. Possibly even Switch 1 connected to switch 2 and switches 3 & 4 connected to switch 2, anything to break up that long string of switches. Normally you don't want to daisy chain more than 3 switches.
Better yet would be to get stackable switches, but they can be more expensive.
Are you sure you have stackable switches? Most stackable switches are managed and have control ports on the back so they can be linked together and act like one big switch instead of a bunch of independent switches.
If you have them all linked in a continuous line, the first segment get hammered with traffic. For example, I'll use fake 10 port switches. The first switch has 9 computers on it and 1 link to the next switch. Do this for each switch succsively. You now have 2 switches x 9 computer/switch (2nd & 3rd switch) + 10 computers on the 4th (last) switch = 28 computers all pushing data across that 1st link between switch 1 & 2.
Now if you were to hang 3 of the switches off the 1st switch, each lan segment between the first switch and the next switch only has to handle 10 computers each. You can do the math for other arrangements.