The 770 is quite literally the stuff that doesn't make the cut for the 700s. The problem is, unlike say the wine business where they take the stuff that MIGHT JUST NOT be 100% up to par for the $50 / $100 / $1000 et.c bottle, and label it different name and charge $8.99 AND YOU GET AN AMAZING bottle for the cheap, in this case we are talking about potentially broken or damaged or literally not 100% good to go parts/worksmanship/finishing etc.
As my esteemed colleague above me noted, it probably isn't what you want to hear but in this very forum and many others the same stuff over and over gets posted about the 770. I remember thinking about it myself in early 2010, the cheapest 700 at Dicks Sporting Goods was the 700 SPS Varmint for $500, for like $339.99 they had a 770 that looked EXACTLY LIKE the SPS Varmint, also came with a scope and the military-looking green stock, just a little smaller. EVERYONE TOLD ME NOOOOOOO don't do it, I am glad i didn't because I read nothing but things posted similar to your own experience and much worse..... And the money I spent last fall on my new 700 "AAC-SD" is money well spent IMHO.
Besides they just came out with the new rifle, the 783, which is supposed to be less than the cost of a 700 but close close close to a 770 and newer technology anyway?