I found with mine, I had to be very careful to get the hole lined up with the vent hole. Just a bit off and it would 'suck hard'. If lined up well, it worked very well through my .070" vent. On pulling the rod up, then pushing the rod down hard a few times, you can get a good 'head' of water above the patch, and this helps draw water right up to the muzzle, then another hard shove and blasts the fouliing off the breech as well as cleaning out the Chamber's vent's 'cavity'.
Daryl