Nephilim7 wrote:
Sorry I took so long to respond. Didn't want to tell you the wrong thing from memory.
With disassembled bolt carrier group, make sure safety is off. Cock hammer to make room.
Hold bolt by stem as if it were a rose.
Turn the rotating head ccounterclockwise until it stops. You will see that many of the flat surfaces between the two pieces are now aligned. The bolt must be kept at this relative position between the two parts for the reminder of reassembly.
Hold the carrier in the palm of your hand with index finger along the piston pointed upward. It helps to have last few fingers on either side of the charging handle - it should happen almost naturally. Insert the bolt stem-first into the hole in the carrier. I'm obviously describing to insert so the bolt face will be under the piston part of the carrier if the group were to be turned level.
While bolt is in place, with carrier piston pointed skyward, rotate the entire bolt (leave the bolt pieces aligned) clockwise until the timing lug of the bolt stops in the timing channel of the carrier.
With these in place, hold the group level with the ground with piston at 12 o'clock. Help the bolt to slide forward in the timing channel while rotating the two pieces together. The bolt will rotate as it cams forward and comes to rest in its forward position. The extractor will be near the 1 o'clock position with the piston facing away from you.
This is the orientation required for insertion of the BCG into the receiver. The rest from here is for right handed people. If you are a lefty, adapt to find your own way.
Place middle finger behind charging handle and index finger in front. Press forward on the left side of the bolt head with the thumb. Now the assembly is ready for insertion.
Start the piston into the gas tune. Then, slide the assembly forward to stop the rear just in front of the rear trunnion (part at the back of the receiver that gets smacked by the carrier during fire) . The locking lugs of the bolt (your thumb is pressing against the back of one) will be just above the receiver rails.
Press down firmly (you are depressing the already cooked hammer as well. Make the lugs ride the rails as you slide the BCG into the forward position until locked and fully forward. The bolt tail should be the most rearward part of the entire BCG at this point.
It is best to let the hammer down with your left thumb pressing from the front and right hand pulling the trigger. The hammer will rest against the bolt tail and hold the assembly securely in place. Otherwise, the assembly is prone to falling out when the barrel is pointed up. Not what you want.
Then, insert the recoil assembly into the top rear of the carrier and press it forward, loading the spring, to allow the recoil "keeper" to rest in its channel above the rear trunnion.
Close the dust cover and do a function check or two. Done.
That was really hard to type on my itty bitty phone! Hope it helps. Let me know if you need elaboration or more specifics.
Let us know how it goes, OP!

First part really helped, clarified that I needed to turn the swivel part of the bolt all the way counter clock wise.
Second part, I tried to consolidate with the video you sent, at the 3:00 minute mark the guy points the piston part of the carrier downwards after inserting to demonstrate how the bolt will slide down the channel and stop on it's own.
I admit, I'm making this more complicated than it should be lol. But I saw the first attempt when I had it in, and slid the carrier in with the bolt... it scratched up a lot of unpainted things, tore up the bolt a little too looks like, lol... no real damage, just scratches...
I wanted to give ya a shoutout Nephilim7, thanks for your effort in trying to help me with this thorough walk through, especially considering that you wrote it on your phone!
As of now, the Vepr12 is still in pieces, I ended up spraying the bolt with a little bit of CLP, it was getting dry from me handling bare handed and leaving it out for this long, I remembered being a little more lubed when I first took it out, so I hit with some CLP... also slathered just a small dab of Redline Synthetic bearing grease in the channels of the bolt carrier where the bolt runs through.