I have the .25 acp breach plug but have not used it , because the Rem. klean bore primmers are working great and I have ""NO"" blow by at all . The last time i shot , the back of my breach plug was spotless , even after shooting 30 loads , not one speck of anything. I have never had a gun stay this clean . My Tradition pusuit shot great , but the klean bore primer were to short and i had blow by , and for some reason the 777 primers were the worst i ever shot . I had so much blow buy that after 1-15 shots i has so much crud around the breach , that my Puresuit would no longer stay closed until i took it aprt and cleaned it. I saw a thread once , where someone had measured all the primers and listed them from shortest to longest and also the coolest and hottest burning . I wish i new where i saw that .
hear is some info on primers strengh ,but does not have the lengh.
http://www.hpmuzzleloading.com/Technical3.html