Yea, with the i5 2500 the chip
can only be overclocked to 3.8GHz. It can turbo past this, up to 4.1GHz, but this is with only one loaded core. For the sake of our comparison we usually disregard turbo as not "real overclocking" so the maximum it will hit is 3.8GHz.
You could get an extra ~7% by increasing the BCLK, but taking into account the risk with such a small gain (maximum clockspeed 4.066GHz) I don't judge it to be worthwhile.
4.4GHz may be achievable for this overclock with turbo mode (1 core) but I certainly wouldn't say you could overclock an i5 2500 to 4.4GHz. Instead, 3.8GHz is as far as you can/should take that chip IMHO. If you want to overclock so much that you are raising the BCLK then I would suggest just selling the 2500 and picking up a 2500K for a small overall outlay (then overclock just with the unlocked mutli, BCLK at 100MHz).