My question is? If a person was to shoot T7 powder only in a knight45 or 50 cal rifle what factory breech plug design do you think would be the best. The FPJ with the cavity at the end , The power stem that is hard to clean or The domed Revolution plug with the smaller inlet nipple opening and smaller flash hole

777 ignites with out to much trouble with any of them since going beyond that point depend somewhat on the vibration characteristics of your particular barrel the only way to find out for sure is to group shoot with your favorite load with all of them.

The older domed NFPJ plug was supposed to reduce the fouling but ive never tried one. I have one but never tried T7 in mine yet. The FPJ plug works fine but it is dirtier and the flash channel is small. Keeping it clean is the only issue with it IMO.

I prefer the new NFPJ conversion the best regardless of powder and preferably the original Lehigh GenII which is no longer available. My main reason is because they are so clean and the flash channel will need less maintenance.

GM54-120, I did purchase 2 of the knight/lehigh breech plugs one my .45elite and onefor the .50 LRH that i have been putting together for a while.( I have basically bought it one piece that a time.And as of how I still have not got to shoot.) I had it in a elite syn stock but i have just purchased one of the new shadow gray thumbhole stock that knight is now offering.
In my .50 master hunter and my .45 extreme I have only used the FPJ with the cavity in the end of it with pretty good luck but like you said it was dirty. That is why I was wondering if one of the other factory breech plugs might work better. I had read that the revolution dome plug was suppose to reduce fouling and blowback when useing T7 but after looking at the nipple and flash hole in the one I got I just didnt know.

will the new stocks fite the older knight barrels are is there work needed

There is no work needed ,It was a bolt in job ( It was made for the fork lug ).