I've had the same problem as you it seems. I was unable to OC past 4.3 @ 1.185v. Always BSOD after going any higher, and no matter what voltage I used I was unable to get it stable. I've since given up and stayed at 4.3GHz. I think it comes down to some CPU's can and some can't ah well.
I actually made a thread about it a few weeks ago, if you look at my profile try and find the post I think it's titled 3770 OC Help. Maybe you can find something useful in there... let us know.
Vcore could be drooping under load, which upping your LLC (loadline calibration) setting can help with. Careful with this one because under higher voltages there is the potential for extra 'wear' on the CPU due to voltage spikes when the load changes. I'd recommend using the lowest setting you can get it stable with. I think mines on 'normal' LLC with 1.21 Vcore @ 4.5.
Also might try nudging your VTT voltage up a bit. I think its called VCCIO on some boards.
What can I say after couple of days with testing. 4.2 Ghz is max what i can set stable. Sad but true. I have very bad chip as well. 4.2 Ghz with 1.150v is stable like a rock. Could be run faster all the more that i have custom WC. MoBo is good for OC , RAM too. Most of 3770k users can easy run it at 4.5 and faser with 1.2v. Btw thanks for advices and opinion.
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Mine is at 4.6GHz, 1.185v, .01 voltage offsets, load line calibration at default, multiplier set to PER CORE not all cores, Turbo Boost Off, All C stepping stuff enabled & is a Costa Rican chip. Just some setup info. I can get more specific when I get home if anyone has any questions.