I don't like to put more contact on the barrel, It has to do with harmonices. Please don't ask me to explain those. lol . I just can't see more presure on the barrel I'd make it fit tighther at the rec. What are you going to do this on and is it going to be the 7.62x54 or the 7.62x39 maybe I'm missing something.
My understanding (I haven't read the entire thread yet) is that in the absence of a free-float barrel setup (the better solution), the bedding will not INCREASE accuracy, but will make the grouping more consistent because the pressure against the barrel that the handguard imparts is more precise and therefore more predicable. It kinda "locks" the handguard into the same spot.
Things like bipods, etc. can really hurt accuracy. When I start a Romak build, I'm going to seriously investigate how to put a bipod mount on the receiver, like the SVD's bipod mount. I hope to make it a bolt-on ordeal but it may require permanent alterations, based on pics I've seen.
The harmonics would make perfect sense if you watched the gun fire from one of those high-speed cameras, where it films so fast it looks like slow-motion. You'd see the thing whip all around and look like it was falling apart!
Think of it another way - if you are pushing on a real heavy object, like moving an engine in the garage, or something like that, you could lean on it and "rock" it along the floor, and your leaning pressure would make it walk along... that's how the movers got my 600-lb gun safe into the corner.
Well, the handguard imparts that same "pre-load" onto the barrel, and so every time the gun fires, and violently recoils, the pressure from the handguard is pushing the barrel around, causing the grouping to open up.
Cryo treatment helps in that it aligns the metal more tightly, so this whipping motion is more likely to return to "true". Comparison of swinging a tree branch around the size of your finger vs. a broom stick. Both whip, but one less than the other.
I am parroting all of this from from past reads of the "experts", so if anyone has more info, I'm all ears!