Thank you for the replies.
In normal operation the output current is below 2 A.
The problem is the short circuit protection... I want it to survive a 1 second accidental short circuit, rarely, not continous. I used a 0.1 ohm resistor for current sensing because I had it, I will get a 0.22 ohm that should limit at 3 A.
I should mention that after the short, the heatsink is cold, it's just a problem of too high instantaneous current, and I don't understand why it's not limited.
Can you recommend a more suitable MOSFET in TO220 case? I tried IRFZ44, with the same result.
Thanks again