My test model arrived today while I was out shooting the Rem. This conversion is to reduce the blow back in the breech area of the Knight DISC.
First remember that this is my first experiance with a NFPJ lehigh or knight. I really do prefer the FPJ - so this was all new to me.
The breech plug looks some what like the FPJ - it has a concave end with a removable vent liner installed. This breech plug will not work with a Knight primer adapter the pocket in the Knight holder is not quite deep enough. So you do need to install the Lehigh primer adapter.
Speaking of the adapter there are some difference in construction there also. If you look at the picture you can see one of the difference in that the exposed wall of the adapter has more metal and will close the gas port when the bolt is rotated down. This gas port is where the hot gas was coming from that burned the bottom of your scope.
Once the system is installed and the bolt is closed it seems to be a bit tighter than the Knight system.
When you insert a primer and close the bolt you can feel the primer being pushed snugly into the the tapered wall of the breech plug. It is a snug fit and should provide a decent gas seal.
Extracting an unfired primer from the plug does require more than a little finger pull on the bolt to extract the un-shot primer.