Myself, i have no experience with the Encore, so i have no first hand knowledge of issues of that rifle. What i have done to cure blow back in my rifles is reduce the head space 3 different ways.

The simplest is to use an o-ring. This involves using a drill to make the primer pocket some deeper, so the rifle will go into battery with the o-ring in place. One needs to 'sneak' up on the correct depth. Drill too deep, and there will be no seal, and the innards of the primer will walk out of the cup when fired.





The o-ring pretty much seals the area at the base of the primer, when it is compressed, and is good for 25 or so shots. This works.





Another thing i have done, was suggested by Screwbolts, when he pointed out that my breech plug had flame cutting in the primer seat. This involves drilling and tapping the breech plug to receive a 3/8 x 24 grade 8 bolt.





One can then make the primer pocket less deep so that when the rifle is put into battery, the primer is crushed ever so little. This creates a 'seal', and has reduced blow back to zero in one of my Omega.





In my Accura what i did was make a breech plug from a grade 8 bolt, and by making the head space some less than factory, was able to reduce blow back to near zero.






The CVA breech plug is on the left. The length of the home made breech plug with the primer in place is about 0.020" longer than than the length of the CVA breech plug with the primer in place. This results in a crush fit when the rifle is closed, and hence reduces blow back.