max bluetooth baud rate on UNO ?

the arduino UNO official doc says the max baud rate for Serial is 115200, but many sources indicate that the max given by the chip is actually much higher (1Mb or 2Mb)

the SmirF bluetooth data sheet says the max (under normal SPP mode) is 240k (HCI mode is even higher), so I tried 230400, and 200000, but it couldn't establish a connection on bluetooth. 115200 and lower does work.

btw I'm using the hardware Serial to connect to the Smirf module, and I unplug the USB when the board is working, to avoid conflicts on the Serial circuits.

I saw many reports that people achieve 230400 speeds on Serial and bluetooth, how did that work? (I didn't even get any random output on the bluetooth receiving end)