IPhone 5 A1429 Downgrade to iOS 6?

I'm trying to downgrade my iPhone 5 A1429 but every ipsw I download iTunes says isn't compatible A1429 model is a gsm+CDMA model but I asked apple what my phone was and they said CDMA but I can't find a Ipsw that works for it and iTunes accepts it I'm running iOS 7.1.2 and want it in the iOS 6 i've tried many ipsw or firmwares and none have worked please help!

You can't downgrade your iPhone. As of iOS 7, Apple has made it impossible to downgrade you device. Sorry.

The only way you can downgrade is if:
You are on iOS 6 with SHSH files, or
If you are using old hardware (iPhone 3G and older).

Not possible