Originally Posted by
Semisane
Have you ever tried a shim between the face of the breech plug and the barrel shoulder rather than under the primer?
Long ago been there done that...
But then you a moveable-looseable part that you have to keep track of, plus it makes it much more difficult to put Teflon tape on with a moving part.
The 0.248" shim is the best thing I have found... They also make a 0.174 shim with a larger choice is thicknesses to get the exact fit if you can not get it done with the 0.248 shim. Just put the 0.174 in first and then the 0.248 to hold it in place.
Once the 0.248 is inserted and pressed down it is not going anywhere.