Face off existing probe, center-drill it, and then drill a wee hole a half inch into the probe.

The extended probe is made of very stiff stainless steel wire tightly twisted and then cut to length.

I bent the end slightly and shoved it into the hole -- it's held in place by friction.

The piece above the bolt is a stainless probe extension that looks nice but interferes with the flow of CO2 past it. The twisted piece of wire below the bolt shows how much I bent the LoopSnoot base before inserting it in the drilled bolt. All in all it was easy to do and it works great -- even if it does look a little strange.

WhiteWolf:
Now depending on how fussy you are for pellet loading My results are .330 Thou measured from the front of the o-ring groove. This is ideal for all the 22xx guns 13xx as well. For the open throat of the 1400 150 180 etc from same point for measuring .440 thou. This is using a 5/64th drill bit stock. The main idea is to get a dose of liguid Co2 into this area so that it acts like an expansion chamber and get your intial expansion here before it's travel down the barrel. As for the older style Cr bolts that have a probe cylinder with a matched port in them they don't allow for the expansion because they take up too much space. The 5/64th drill bit stock is more than strong enough to push the pellet into the rifling and it will hang up on some of the English Webley ammo. But I have yet to find a gun to shoot this stuff accurately then maybe I can get rid of some of what I've got. All this info is designed for the .22 cal and it does work for the .20.