Tuning Breech Seals

i used one from a universal ebay oring kit the last one i did .. it wasnt exact and seemed alittle too tight but i found it 'took a set' to the bolt pin pretty quick and worked fine .. might work is all im saying .. those kits are cheap and handy anyway for other things around the house you cant lose lol .... id just get the cheap black rubber ones though and avoid the silicone ones, doubt those will conform as easily if theyre slightly oversize etc...