You might have better luck with primers if you would switch to W209's. The breech plug was designed for the length of the Winchester. With the CCI the head space is long creating a void that causes extra blow back pressure on the primer - driving the primer back out of the battery cup. I do not believe it is occurring because of you powder load. There are several people that are shooting loads greater than 120 of BH with and 200 grain bullets. But the are also using breech plug with the correct head space. With the Lehigh/Knight breech plug you do not need a mag primer to ignite BH even freezing temps.