I had been trying to install samsung 850 evo ssd on my 2012 Macbook pro. I tried using CCC, installed a fresh copy of el captain using bootable usb; but for each of these, i was able to boot from ssd when connected through USB but when i install it in the HD bay it won't boot. I read a lot of articles regarding this and there are people facing issues like mine but again there are people who have successfully installed the samsung 850 evo ssd in macbook pro 2012 (without retina).
I have already wasted a lot of time on this, any help will be greatly appreciated.
Best Answer
I hope you still ready this - it has been a while.
I spent my whole Chrismas and new year holidays fighting with similar situation.
I found out the main issues are:
MBR vs GPT (please google)
disk letter ID (e.g. C: - D: ....)
use some third party software to deal with partition and disk address
use some third party software to Clone the disk.
Good luck !