I ordered a new .177 probe (stainless) off your EBay store this week. Got it fine and FAST! ... but while attempting to assemble my 2240 with a 24" 177 barrel, I found the probe does not seat to the O-ring. The metal lip in front of the O-ring contacts the leade (metal to metal) before the O-ring engages. I measured with a set of calipers and the metal lip is definitely larger than the bore. I haven't broken out a dial caliper to take measurements.
For comparison, my old .22 probe slides and seals the O-ring inside the leade.