i5 6600k OC problem (bad chip?)

[n3ckol]

Hey. Im new here. My name is Jack and I am from Poland (forgive me please for some grammatical errors 😀).
So, lets begin.
I have msi z170 krait gaming 3x with i5 6600k.
My ram is hyperx savage 2x8 3k MHz cl15 and psu is corsair cx550.
I am trying to get 4,5 GHz on my CPU, but... It crashes when there is 4,3 on 1,27.. :O
XMP profile ON
The only stable value I had was 4,2GHz on 1,25V with tempertures bellow 60 of celsius.
Can you help me a little bit what can I do? Do you need a screenshot of bios settings or something?
Greetings

 

[geofelt]

You probably need to up your vcore.
1.4v might be a good limit.

As of 12/04/2016
What percent can get an overclock at a somewhat sane 1.40v Vcore.

I5-6600K

4.9 14%
4.8 38%
4.7 67%
4.6 87%

On a stress test, 85c. or a vcore is about where you should stop.

 

[n3ckol]

I tried with 1,40v on Vcore with xmp and without. Both error after 2 minutes on aida64. Temperatures get to max 74, and average 68 of Celsius.
Maybe I have turned on some function on CPU which is causing the problem?
I cant belive that I have so garbage CPU :/

Update:
Changed dram voltage to 1.35 (because mother board set manually to 1.36 dont know why).
Change vcore voltage to 1.35 and I get stable 4.4GHz with max 72 degrees on aida.
1.345 was crashing after an hour.
Still bad :/ Any ideas?