So I've been testing this for, well, ages, and its not easy to do. The first time I did it was in my 1:37:34 rekkie for NG Easy, and I did it by accident, leading me to know well, its possible, and it'll save you about 10-20 seconds.

Here's the video for it, yeah its shit quality I know

So my testing has concluded: It takes 10 shots to bring him to the floor. I use 9, reload, and then whatever I've got left. If you drop him before you reload, you lose time, and heres why: When jack goes down he has two counters: A; a damage counter and B; a time counter. You want to run down that damage counter, not that time counter. If you deal a certain amount of damage within that time he'll go for the chainsaw, or if you leave him long enough he'll also do that, but you wont one cycle him.

But heres the kicker, you don't even need the bullets I had in reality, just so long as you do the damage, I've done it in as little as 5 bullets and the rest knifing. (More bullets =/= more damage, as soon as he hits cap he gets up, easily doable with 5 shots and a knife)

Now once he gets up, be careful. You don't really want to slash him more than sort of 12-13 times or his counter health is now too low for head-to-chainsaw action. I normally slash him a couple of times whilst he's getting back up, then let him grab you, and ill explain that in a second.

Then i'll slash him 8-10 times whilst hes opening the cage, this makes prime health level for one cycle. The reason I let him grab me is because in my testing I found that 99% of the time I didn't let him grab me, he wouldn't one cycle, it could be a literal TINY difficulty modifier, but it does the trick for me it seems (then again, could just be unlucky)

So now you've set him up for it. Stop slashing and keep pushing into that chainsaw corner, as soon as you grab it, keep backing into that corner and thrust attack him, he MUST hit you. When he hits you he's going to clip through you and put himself into that corner. When he does, I've found that you can either just thrust attack, or one slash and thrust, the one slashing seems to be more reliable as of recent testing.

Now heres the thing: Do not miss any chainsaw time, and aim for the head after a couple of seconds. If you don't connect with the front of his body or head, a lot of the time he falls down, which means? You guessed it, no one cycle. You want to drive that bad boy right into his skull, and drive it hard.

Now he's down, don't let up, and don't miss any more hits, as soon as you regain control hold those mouse buttons down and thrust thrust thrust. If you don't get every single tic of that chainsaw damage on him within about 0.5-1 second of him going down, no one cycle. You miss, no one cycle, you position him badly, no one cycle.

And remember, he can still take damage while getting up.

Happy chainsawing!

Excellent guide! I will try this out soon, at best I have been able to one cycle him maybe 20% of the time so this is very useful information. And gratz for the new WR :)

Well thanks! At first I could barely get him but I started just whittling down these little things and now I get him at least 80% of the time