my own bottle cut with the factory edge was reletively dissapointing, but I was using a poor technique for the ak47. I was doing a back cut one handed, left to right (right handed) when I should have been doing a push type cut, right to left with both hands. The blade was not heavy enough or sharp enough for its own weight to carry it through the bottles, so I would have had to push it through to make it work.
That could have been fixed by me either propelling it ultra fast (not possible with my level of accuracy), or bring it down to 18 degree's per side high mirror polish. I didn't get to try it before I had to sell it though...
If you mean flexible as in the blade literally curved from side to side as it would when you have it in a vise - not at all. at 3/16" through hardened, I could flex it with my hands bending it over my knee, but just barely