Recoil spring

[Onagoth]

I have seen people on youtube rack their slides by grabbing it from the underside of the gun with the thumb and first two fingers and pulling it back towards the trigger guard.

I have tried doing this with my factory glock, but it doesn't work that easy, is this the result of a lighter recoil spring, and will using a light recoil spring bump me out of SSP for IDPA (I think not, but am not sure)

Thanks