Mosfet performs below my expectations.

[liviu.gelea]

I think I'm missing some knowledge about how mosfets behave.
I have the following circuit using an IPP029N06N

The problem is I expected the voltage drop over DS to be waaay smaller than the 3V it is.
Now my current understanding is that at 5V through the gate, the source-drain should act like a few miliohm resistor but even at 15v I still get a 3.2v drop.
Could someone please shed some light as to what I'm wrong about? Initially I paired 10 of these in parallel hoping to drive enough amps to weld nickel strips. I ended up buying a working device instead
Thanks

[wraper]

You cannot use a MOSFET like that. It will not fully open, as once current starts flowing through it, GS voltage will drop. If you place a resistor in series with drain, not source, it will work properly.

Now my current understanding is that at 5V through the gate

And there will be way less than 5V with your circuit.

[Siwastaja]

MOSFET is controlled by Vgs (voltage between gate and source).

When current is flowing through your resistor, what is your Vgs?

[liviu.gelea]

OH, I'm terrible  . Every time I read "Vgs" I thought about the potential of the gate relative to the ground, which in this case is tied to DRAIN, not source.
Thanks a lot for your time.
PS I'm surprised anything turned on since my Vgs was basically 0.

[wraper]

PS I'm surprised anything turned on since my Vgs was basically 0.

It was not 0, It was slightly above V_GS(TH)