Quote Originally Posted by Gwylan View Post
I've lost count of the number of shots I've put through my S400s. If you have to replace them every 2 tins, there's something wrong. OP, are you sure it's the breech seal? The transfer port Oring seal can leak from around the same area, and it's easily misplaced, or even lost, when you do a rebuild.

Gus
I agree with Gus. You have to be very careful it doesn't move out of position during the rebuild.
Try placing a paper tissue over suspect area then dry-fire and watch the tissue for movement.