If it leaks down the center of the bolt its the 14/70 or the 18/70 on the bolts stop.
If its leaks around the outside of the bolt then its the 17/70 on the inside of the breach.
Put your finger down the breach and plug the bolt tip up with the tip of your finger. If it builds up pressure then your leak is because of a bolt stop orings and if doesn't then its because of the inside breach oring.
Hope this helps.