I am having problems with my Jamisen 256 win mag brass. I am using one of the small LEE Hand Loaders, The first time I loaded the new brass it worked great. When I tried to load it again the bullet just falls out. The barrel is a Match Grade Machine contender barrel. I have heard that most chambers are now cut to use reformed 357 mag brass which is thicker in the neck than the brass I am using , does that sound possible? What can I do to correct this problem besides buying the resized 357 mag brass ? Thanks