Yesterday my wonderfully accurate, reliable and consistent 600 started spraying shots two'ish inches low and an odd report; I didn't even have to use tissue paper over the breech to tell it was venting.
The compression chamber was holding air well, even over a couple hours, and the barrel breech seal (o-ring) was fine. This left the transfer port seal in the sliding breech, a tight fit under the breechblock. Inspection showed it had hardened to a crumbly yellow and was chunking out. It almost looked like old hardened varnish. I believe that was the original seal material so if not actually original to the assembly it was the same used as replacement (the 600 intro was 1984 iirc). The barrel breech o-ring is the newer blue material, probably replaced not too long ago before I got it (2yrs maybe?).
If it had been resealed within I have no way to tell without full disassembly, and truth is I did not want to do that just now for just the t-port seal. Im hopeful that it may have been resealed not long ago and not replacing the t-port seal was an oversight (can I be That lucky?). Fwiw, the proper way to get at this is disassembly of at least the stock from barreled action and separation of the trigger group/action from the barrel/pump/compression chamber (even if you don't disassemble the pump stuff).
SO, thinking about this I concluded I could pick the old seal remnants out from the opened breechblock with a toothpick. This went well enough but I did not know there was a thin shim? washer beneath the seal, perhaps to adjust the seal height/tension. It fell out and under the breechblock
. Enough for last night......
Today I went at it again. I was able to hook the shim out with a thin brass wire diy 'probe'. That took more than a little finesse.
A quick spray of low pressure air, a film of FWB Special Grease on the new generation t-port seal and I was barely able to get it in, under, seated and in place (more toothpick work) in the bottom of the sliding breech. A film of the lube on the ramped exhaust port surface and done.
Test firing passed so out to the back deck rail.....a few warm up shots and back to the dismal paper target of yesterday.
I win
, futzy work but it can be done.
