This seams to be a much discussed topic as of late.
Here's my take "For What Its Worth":
(1) Breech seals are cheap and the most common failure on 97s, so change them often and and don't expect them to last forever. They don't. I've seen some guns that need replacing ever 500 rounds for various reasons.
(2) Easiest way to check to see if one is toast or if the gun has "issues" is when the gun is cocked put your thumb on the compression tube and see if the tube can be moved around easily. If it does the seal isn't being held firmly against the barrel and is probably leaking. It's not totally uncommon even with a new seal installed.
Paul Watts
http://www.springgunning.com 
