It will either move around,or if you look the edges of it may be lifting up,causing the breech not to sit properly, either way it is the best way to start as it is the simplest,and cheapest
, Jamie is right,if it is in good condition a few people lift it out, clean all the adhesive off,the glue it back in,as long as it is in good condition there is not really a need to change or replace the breech seal at all ,so gluing it is ok ,in my own opinion .